Most of it

While blowing one and stroking another, you use your free hand to grab the chalice. Holding it first to the one you are stocking, you feel it tighten just before it blows its massive load. You manage to catch most of it, filling the chalice a third of the way up. While you were distracted by catching that cum, you don’t notice as the cock you are absentmindedly sucking suddenly cums as well. Startled, you swallow some, before you realize what is going on and try to catch the rest in your mouth. It tastes amazing on your tongue, and you don’t want to have to spit it out. But you are in this to win, and you spit the remanding cum filling the chalice to the halfway mark.

You begin to work on the massive third cock you had paused on, stroking with one hand as you suck on the tip, holding the chalice in your free hand as you work. After a minute or so, you feel it tighten and are able to catch the massive load in your mouth fully this time. After a few spurts as you stroke out the last of it, you spit the cum into the chalice, filling it almost to the brim.