i bought thr 5 gal, 7 bag system last year and can honestly say they're a godsend! you don't need all 7 but i can't see how only 2 will do the trick...perhaps a few details? anyway, the 5 bag system is all one needs.
it's different from screens as it's very wet when separated and is very easy to mold into whatever shape you want before drying while the screen method results in more of a kief product. plus it's a helluva lot easier to separate with the bags.

if i were you i'd save those fan leaves along with those loose, lower buds and wait until a bubblebag system came along. put your trim in the freezer and it'll keep until you're ready. you can sometimes find them at gypsy's auction site and save a few bucks...
www.seedbay.com
it's where i bought mine ($285 incl s/h) and worth every penny...have already made over 3 oz's of high grade hash! plus it's the type of thing where one can go in with a friend or two and share the cost.

good luck with the upcoming harvest! i'm about a month behind...