Equal amounts give good work time and proper hardening. Lack of proper hardener will cause slow curing time and possibly not cure at all if not enough hardener.
I mix it by applying a dollop of the black resin and along side a dollop of the white hardener trying to get approximately the same size dollop from each tube. Then thoroughly mix to a uniform color and apply. It does creep quite a lot before hardening, so best to have the part that you are gluing level, then watch for excessive creep. It wont hurt to screed it back in place if it is still liquid but don't move it if it is already starting to cure.
I use JB Weld on lots of things but it has it limits as to what it will stick too. Some types of thermo-plastic wont bond well with it.
My favorite mixing pot is a small plastic container that my scotch brand black vinyl tape came it. The hardened resin can be popped loose easily (note that it is one of the types of plastic than doesn't bond well). Softer plastics like PVC can sometimes bond well. I fixed my tractors fuel tank 7 or more years ago and it is still holding.
