Can Frenching be done on any subject?

 Can Frenching be done on any subject?

"Frenching" appears to be a typo; did you mean "freelancing"? If so, freelancing can cover a wide array of subjects and industries. It includes fields like writing, graphic design, programming, marketing, consulting, and more. Essentially, if there's a skill or service that can be offered independently, there's likely a freelancing market for it.