I think I don't understand what you mean by process. I just tell the LLM what process I want it to follow, e.g. follow the plan document, use cheaper subagents when appropriate, respond to PR comments before merging, etc. It's usually a short paragraph.

I do use skills for other things, I don't believe that skills are bad. I'm just not sure what they add in this case.

That short paragraph is your skill, essentially. It's the way you like to work, or the process that you like to follow.