please help an old man here. maybe it's true you can't teach an old dog, but i still want to learn.

i've broached this subject here before. czech nymphing. please explain something to me. in all i've read (including trying to read the articles on faol), there is something mentioned in the technique involving leading or pulling the flies.

is this not creating the dreaded "DRAG" i've always heard was such a bug-a-boo in fly fishing? i have yet to actually witness someone using this technique and am unable to purchase books or video (fixed income) so please, will someone try one more time to help me understand.