I'm going to get in trouble here, but here it goes .

I use MAS epoxy (cold cure) and the pumps supplied. I have never mixed a bad batch (yet - touch wood), no matter how big or small the size.

I don't weigh cups, or measure the epoxy out into specified size cups. I pump the resin and hardner right into a "cottage cheese" or similar container and mix thoroughly.

If I need a small batch, I might use a smaller pot, or even the lid.

A couple of things that may help here:

1: Dumb stupid luck.
On the other hand, I've made three boats, and as a general rule, dumb luck (mine at least )doesn't usually last that long!

2: I use MAS epoxy.
MAS epoxy uses a 1:1 ratio between the resin and hardner.
This makes it really, really easy to squirt to a couple of equal size puddles of goo into a lid or other shallow pot for mixing. Need twice as much? Make four puddles (two of each) in the lid. Using an epoxy with other ratios might be more difficult.

3: Cold Cure epoxy
I use cold cure epoxy rather than regular or fast cure. This means that "blush" is not a problem and it has other uses, see below...

4: I warm the epoxy, even when the room is warm.
I keep my epoxy in a little styrofoam box (pictured below) that has an old tea towel over the front. There is a light bulb and a small fan inside with the epoxy. I turn it on an hour or so before I go into boatbuilding mode. It almost runs out of the pumps on it's own...
Of course, as I said, I use cold cure epoxy, which has a long cure time. If I did this with regular or fast cure epoxy, it might boil in the mixing cup.

5: I try to be nice to the pumps.
I press slowly down on the pumps and when I have squirted as much as I need, I reduce the pressure to let the pump come back up. I don't take my hand away and just let it come up as fast as it wants though. I guide it, so it doesn't suck too much air and caue it to burp the next time around.

I think that's it. Flame on folks!

coop