Fuller's the man when it comes to AKs. One thing he didn't point out when he was talking about the safety impinging the disconnector on removal was that the one he had in the mockup is a full auto disconnector - you can tell by the bobtail sticking out of the rear of it. Nowadays it's rare to find a bobtailed disconnector in newer rifles. Another thing that will cause your safety to be tight as frog snatch is using an aftermarket retaining plate (in place of the shepherds crook) they tend to cause tension on the safety by the way they engage the lever.
Another good area to look at is the back of the bolt carrier vs. the hammer face. A lot of early WASR bolt carriers would hang on the hammer at the full rear position and were a PITA to cycle manually. Normally they will eventually wear in but it's not hard to polish the backend of the bolt carrier to get that smooth action. I balk at doing anything more than a slight polishing on the hammer face. Whatever you do go slow and make sure you don't take too much off. If you do your hammer won't lock and the rifle could double or have an OOB.
There's some good tips and tricks on this page:
http://www.novarata.net/Linx310/index.shtmlAnd FYI - if you're looking for the best deal right now in steel AK mags these are the bees knees - slickbacks so you don't have that damn ridge cutting into your palm.
http://www.aimsurplus.com/product.aspx?item=MAK47E30&name=Surplus+European+Steel+AK47+7.62x39+30rd+Magazines&groupid=15 I've bought tons of these and they're damn good mags.