All that has been said about partial panel is true. With my own (limited) experience I'd like to stress that you should never, on partial panel, try to make more than one adjustment at a time. Learned that lesson the other day when I did a partial panel lesson after about six months off the instrument flying. Spent five minutes trying to hold a fixed descent rate with wings level - without success.
Then gave up on the descent rate and concentrated on holding the wings level. That worked things out.