Unfortunately, no tricks to the shot glass method. You're seeing exactly why you need a good test kit for just such situations as the one you're experiencing. But, at least you've got one coming, so you'll be in better shape soon.

I think you're on the right track being conservative with the chlorine additions (using the higher FC readings as your basis for bleach additions) until your test kit comes in and you can get more consistent FC readings.

Perservere and bleach will get this cleaned up for you. Good luck.