In this video we cover how to do your own 3-angle valve job on a Mopar Slant 6 head, but really it's the same for any engine, from a lawnmower to a big block. Doing your own valve seats really is no more expensive than having a shop do them, and with the quality I see out of machine shops today, I trust my own work far more than theirs.

Links:

Source for Neway tools (not sponsored or affiliated):
https://www.cylinderheadsupply.com/

For a slant 6, I ordered Part #'s CU234 and CU205
If you have a different application, the size guidelines are here:
http://www.newaymfg.com/cutters

Marking fluid: https://amzn.to/3uoUD2M
Lapping compound: https://amzn.to/3E0VES2
Lapping tool: https://amzn.to/3E0VES2