Almost worth getting a bunch of business cards made up for all the things that you do yourself, rather than paying someone else to do, and hading him one of those for whatever the subject at hand is.
Could even get ones with a "fill in the blank" for the subject skill.
Of course you certainly don't have to accept any "work" he might try to get you to do.
Could also get cards with "Super Genius" on them.
[ATTACHPrint ACME SS DIYer since . . . Cards and better yet a sign proclaiming same along with No Trespassing or Soliciting. Violators Will be prosecuted. Post on driveway entry, outside of shop and have a good time with the next visit.
I'd spend some time talking to the guy to find what makes him tick and then decide how to proceed if any further contact is warranted or cut off completely.
Some folks are just too obnoxious to waste any time on understandably.