Free spool mode! I keep the rod in my hand when I am dropping. Two reasons: (1) I can better control the amount of line by thumbing the spool and (2) if I get a fish on while lowering the ball, I can immediately reel the fish tight.

When you get the ball to the desired depth, you shouldn't have a heck of a lot of slack in the line. At this point, you may still have a little winding of line to do- this is ok. Wind down until it is tight and then use your hand to bring in the minor stuff the drag of the reel can't handle. This touch is going to take some practice and experience before you have it down. Many people are under the misconception that the line has to be straight down and the rod bent like a pole vault..
Actually, you want some blow back from the mono... (1) creates less pressure on your rod, (2) stretches the mono without damage thus helping you hook fish once it hits. When a BM or King hits, they actually turn to one side and downward... the stretch in the line will recoil to original shape offering no slack in the line at this point.

As far as adjusting depth, depending on how much deeper you are adjusting. Anything more than 10', you'll probably want to grab the rod again- remember those can hit at any depth. Just a couple feet.. just free spool/thumb a few feet off the reel...