I played around with some foam the other day. I used a 1gal bucket, placed an oversize small trash can bucket in it.
measured A and B in two seperate qt containers.
Put A in the bag/can, added B and stirred, pulled bag up and out, snipped bottom of bag when I got over to the hole that was getting filled. Squeezed everything out and tossed the bag.
Worked great and was not a mess at all.