Not a slam, just an opinion from someone who has been working a very long time , older, cranky and has little patience.

I would hand him the whole thing or just ASK him, nothing I find more annoying than people trying to do my work their way.

I either charge more or won't do it if they want to be helpful.

If I am doing the job then I will do it my way, if you don't want me to do it my way then do it your way or get someone else.

Rant over.