Well just about any olylift from the floor will help the squat some - due to the leg action and explosion. Though I think the power snatch helps the most due to the greater lean over and speed.
I read about some coach saying that he sometimes has his athletes, stop squatting for 6-12weeks and just do power snatches, and when they come back to the squat, it has gone up a good amount.
Straight arm low pulls would help a bunch - I did these with a 3x3 after my squats a few weeks back for a month and that was when I jumped my squat from 315 to 345. But it wasn't the only thing I did, but I think it helped
any sort of olylift and straight arm pulls will help the deadlift. But you dead sumo style which maybe won't help as much.
benchpress, well only thing would be power jerks - jerk with a 2 legged dip catch.
jerk heaves - propel the bar up with leg/shoulders/arms and then let it land back on your chest, bend legs to absorb the shock - not as bad as it sounds if the weight is heavy enough so that the bar doesn't go too high. Some carry over to the squat I'd imagine due to plyo leg action, if done for the leg power, then just use the legs to thrust the weight up.
But really a push press would be better due to more upperbody use.
Your better off with explosive pushups that propel your body off the floor in sets of 3. I'm trying these right now, complexed with lighter speed/power type bench sets. 2 mins rest between each.