I always put a spark plug loosely threaded in on the side I'm working on. This creates a little resistance in the cylinder changing pressure and helps prevent the crank from rotating while you're working on it. Halfway-ish in, do it and you'll get a feel for what I'm talking about. Helps hold the pistons at TDC because with all the weight up there the crank loves to rotate the weight to a lower position. However, you will not be able to see the piston so you have to rely on valve movement and crank position markings.
I'm having trouble visualizing how adjusting the tappets would move the crank but I imagine it might have something to do with them being quite tight from not being adjusted in a while.
~ Derek
