First off, if you can find it, get this book.

Silver Gelatin - A User's Guide to Liquid Photographic Emulsions by Martin Reed and Sarah Jones

It will even tell you how make a variety of your OWN emulsions. So this is probably something you might like.

It also cover coating, etc.

As to the AG Plus.....

I have heard it is markedly faster, although I have not used it myself yet. The Ag Plus is supposed to be faster. So says Rockland.

If you do get this stuff, get it from a store if you can!

I know this may sound odd, but all of the Rockland products get FASTER as they age. So fresh is bad here. Try and find a dusty old bottle in a store with slow inventory. With online suppliers, they may be simply booting the stuff on from Rockland the second they get it. Nice and fresh. You may also want to stock up and store some for 6 months or so.