to get real good you need to measure everything. using a small 6 oz cup for small batches, say 3 oz or less. you then know how many drops of catalyst you need. i personally wing it, i know i dip a spoon in the resin twice and i need 10 drops of hardener. if its cold i use more, warm i use less. once you do it enough you can wing it too, but you will sometimes screw up.
unless you are brushing or rolling large areas you should not mix more than 3 oz anyway, it will cure faster than you can use it.
for small batches you need to learn something like i do, maybe a spoon full or 2, then so many drops, if it goes off too fast next time use less drops
Measuring is always my issue. I guess I need to buy some cheap measuring spoons and then learn to count to 12. I have got quite a bit of gelcoat work to do, mostly small spots where the PO had placed fasteners. Thanks for the info!!