from time to time I like to go bup. They are challenging , a bit for grip, for stability and equilibrium. They require focus. I use(d) it in almost any kb move. A really great move is just the clean, the instant transition from dynamic moving object and body to tight body and static bell. One can work up to a really heavy bell with some practice. an important aspect is to be not afraid, to let the bell go when it is uncontrollable.
a whole new level is double bup work. then two eyes have to fix two bells instead of one.
As for the press, I worked up to a "not owning" bu press that was very near to my "own" one arm max. But all in all, bup work is more a spice than a main dish. The bup groove on the press can be slightly different to the standard press, especially the lockout, as you usually have to look up to the bell in order to stabilize it better, the bell and hand is more in front of the body, whereas on the standard press the hand is over the hips and shoulders, and the bell is a bit behind.
When you want to build up your press, press a lot traditionally, and may work to get your bup close to that.
A few reps for warm up would be good option, sparks focus and CNS, automatic recruitment of all the muscles . To enhance this skill rapidly, GTG works really great.
