2 part epoxy has 2 separate components that must be mixed together before application. After mixing (according to the manufacture instructions) you will have a limited amount of time to use the epoxy. After this time the coating becomes unusable, typically 6-8 hours.
One good epoxy is Pittsburgh Aquapon. This is a water based epoxy and it does dry fast. The only problem is good epoxy paints are expensive, retail about $140-150 per kit (2 gallons- 1 gallon part A and 1 gallon part B for the Aquapon). There really is no cheap epoxy.