Epoxy works on wood to wood, wood to fiberglass polyester, fiberglass polyester to fiberglass polyester, Metal to metal, wood to fiberglass polyester. Some plastics can present a problem. that is where CA or Acetone can come into play.
So, it depends what materials you are trying to glue together.
It can be confusing.
It can be daunting, especially when you have spent a lot of money and an incredible amount of time on a model and want it to be perfect, or at least for it to stay together.
I hope this is some help.