There are lots of previous posts here and gun forums on coatings applied at home, so you can answer this yourself looking at those and considering what you want to try. Just Google what knife and gun coatings there are and then Google each of those to see how they are applied. There are some you can do in an oven. Simplest option would be simply spray paint I imagine
Sine there's nothing specific to Benchmade in your question, you might try this question in the maintenance section instead to get more answers.