I gotta say, anyone wanting to spray some paint...
BUY THIS SYSTEM
They have adapters for all kinds of guns.
Mix lines right on the cup.
And it allows you to spray at nearly any angle. Because it just sucks the thin cup in as it goes.

I mixed up a gallon and a half of paint in a marked mix bucket.
Then poured it all into those cups, and popped caps in them.
Once in there and capped, normal paint can just stay on a shelf. Activated paint, up to a few hrs supposedly.
I had to mix up 3 extra cups. For a total of 12. But had 1.5 left over.
When the gun sprayed out, just walk over, pop a new cup in, pull the cap, and attach to the gun.
All took about 20 seconds, and I was back spraying on the still wet line.
Pack of 10 cups with lids and caps is $11.