For what it's worth:

Think ahead about everything you want to epoxy and get all parts test-fitted and ready. Have all your application tools ready. Then, mix your epoxy and work effeciently but quickly, don't stop to answer the phone. .

So just plan ahead and get everything set as quickly as you can. Using this method, I don't even use 30 minute epoxy, unless it's something I need some time to carefully set up clamps, etc.

Seems it always goes farther than the amount I mix up, I always end up throwing out a scrap of cardboard with a scrap piece of balsa as a mixing stick hardened onto it, with more epoxy than what ended up on the airplane.