For guitar I usually trancribe cover songs by ear. When I don't have enough time (or when I'm plain lazy) I google the tabs. A lot of them need finetuning, but the general idea is usually pretty solid. Our solo-guitarplayer and I use extended tabs to get ideas across.

As for the fly-droppings: For guitar I find them harder to read than tabs. Especially when chords are displayed as a stack of notes I feel like I'm solving a Sudoku.

When singing my sight reading is getting to a level where I can actually read a piece at real time. Not that I see a new piece for the first time, read it and nail it, but I get the general idea of the part. Then comes the woodshed part of the job