Honestly when it comes to finding hidden packages, I purposely avoid collecting any of them until after I'm done with the main game, or at least until all areas are unlocked and I use a map/FAQ to find them all in one fell swoop. You might find 50 at most on your own throughout the story mode, but finding the other 50 will be a pain because you won't know which ones you've gotten or not gotten.
I did this with the other three GTA's and I didn't feel like I didn't deserve that 100%. You could spend your lifetime trying to find 200 pigeons and not get them all.