Originally Posted by
dsbrantjr
Pushing it by hand will not account for friction in the lower cable housing loop, which is common, nor for "slop" in the derailleur linkage. You also won't have to concern yourself with getting your hand caught in the chain and can better concentrate on the adjustments.
Friction in the cables won't effect the travel limits if they are set too wide, only if they are set too tight and you aren't sure if the chain won't reach the extreme cogs because of the limit screws or cable friction. And, yes you do have to be conscious of where your fingers are when the crank is turning.