Em, not nice to have the same thread in 2 different forums ...

When using epoxy to bond two pieces (as compared to fuel proofing a surface) I make sure that I have at the ready: paper towels busted into individual sheets, a jug of alcohol with the top off, painter's blue tape, wax paper, stir stick, epoxy and appropriate jigs to hold the pieces in place while the epoxy sets up.

I mix my epoxy on a piece of wax paper (rather than a cup - easy to toss) with a popsicle stick.
The paper towel w/ alcohol does a great job cleaning up waste or oops and cleaning up tools before the epoxy has a chance to set up.
I tend NOT the use tape as a boundary as it will result in a hard edge that will be a real B to sand flush but I will use it to keep things straight - like a jig or clamp (thinking about holding fins square, control surfaces straight while gluing hinges, etc.).

Next time - pick a specific forum for a thread.