If you don't have a decent amount of education in psychology already, I wouldn't recommend diving straight into journals...but I wouldn't recommend you don't either. If you want to check them out, I'd say the only harm is the cost and the chance of getting discouraged, so first of all, I'd recommend this: don't get discouraged! You're on the right track. The best teachers are those who still spend plenty of time learning (if only to keep up with their fields), IMO. Educational psychology ("ed psych") is a deep subject—as deep or deeper than many, if not most. In my limited experience as a higher ed educator, I'd say I've learned more about teaching through experience than through what meager training I've been offered, and colleagues of mine who have sought more training haven't had good things to say about their programs...so I'd say you're not necessarily missing much for lack of training, relative to most of us, if you've got a good head on your shoulders, good communication skills, a professional attitude, plenty of respect and tolerance for the circumstances and shortcomings of others, and have paid attention to the teaching styles you admire in your own time as a student. To some extent, training programs mostly teach the basics of these qualities, and can't teach much more. However, I also have a colleague in an ed psych program, and judging from what I've heard from her (I admit I don't have any other real exposure to ed psych on which to base my opinion), I think we've all got plenty more to learn that they won't teach you in the average teacher training program anyway. Therefore I applaud your ambition for self-education, and certainly don't want to steer you away from going straight to the source. I hope I've already disillusioned you somewhat regarding the training you're lacking; it's important for maintaining minimal standards, but in my experience, it hasn't offered much guidance for growth beyond that. If you don't have any particular shortcomings that need ironing out—if you're already a halfway decent teacher—you're probably better off skipping the watered-down, "common-sense" sort of educational psychology you'd get from people who specialize in other things, and who are only teaching how to teach because it's a job they could get.
I would, however, recommend testing the waters of those journals you're thinking of diving into before shelling out the subscription fees. Some journals can be quite dense and advanced reading without a proper introduction (especially cognitive psychology articles, in my experience). This isn't to say you can't hack it, but you may find a lot of articles referring to concepts that are introduced in other articles (or worse, books!) that you can't access for free except through your university, which might also require inter-library loaning (you might not be able to do that without being enrolled, but you should at least be able to get access to some journals by visiting an on-campus library). This becomes quite a lot of legwork, so don't dive in unless you're ready to swim the equivalent of the English Channel. Try looking for free articles from these journals you're interested in (e.g., the links on the right that you can access through a Google Scholar search for "Journal of Applied Psychology"), see how comfortable you are with reading them, and see how far you can follow the reference lists whenever you come across an interesting idea that you'd like to know more about. If you can make a go of it and be happy with what you get out of it, if you're not happy with what you can already access for free by means like Google Scholar or your university, and if you're willing to pay the price of subscription, I don't see any further reason to dissuade you!
Regardless (or especially if these journals don't work out for you), I'd also recommend checking out more introductory literature on ed psych. The thing about journal articles (in case you don't already know this; forgive me if I'm getting pedantic) is that their authors often write to a fairly advanced research audience, so it's not exactly like learning to swim in the shallow end, where most inexperienced students would probably be better off starting. Some books are like this too of course, but it seems to me that most books in psychology are less afraid to belabor their points and more keen on appealing to a more general audience. Especially when setting the average book aside and looking directly to introductory books and textbooks, you can expect to find the process of learning the foundational theories of most domains a lot easier, and probably more efficient; again, I haven't tried doing this with ed psych texts myself, but I'd assume the same is true of this domain as it is of others. In general, the advantage of intro text/books is not just that they're directed at more general audiences; they'll also usually take a much broader overview of the field as a whole. You might have to do a LOT more reading to get the same breadth out of journal articles as you could out of an intro text/book. You'd probably get a much deeper exposure through journals, but if your time is short enough as is, you're probably more concerned with covering all the fundamentals than with sharpening your knowledge on any specific subject, let alone all of them, by yourself!
If you're sold on the idea of checking out intro text/books, you don't actually have to buy anything necessarily. For instance, check out this list of free e-books on ed psych that I just found. To make sure I wasn't tossing you a red herring, I went ahead and downloaded Seifert and Sutton's (2009) Educational Psychology for myself, for free; it looks fairly solid to me at first glance. In any case, it's not your only free option on this list alone, and with a little extra effort or a trip to the library, I'm sure you could find plenty more options for free. If that won't cut it, or if you see recommendations for a particular text/book, consider ordering it used. You ought to be able to get plenty of them for much less than the price of a subscription to the journals you mentioned, which look like they'd run you $\$455$ apiece. I'm a fan of Half.com for used book buying myself. I see some options here for less than $40!
Good luck; I hope you learn a lot of good stuff, and come back to share some of your insights with us here! We could all stand to know more about these topics...Except maybe those who really know these topics, whom I hope will give you some answers of their own too!