Now that summer is here (call it summer, this year the weather has been terrible in the UK), here is my 2c to getting to the point of able to catch and ride bumps on a downwind foil setup where I when this started out I couldn't stand on the board. Based on my very limited experience these were things that stood out.
Definitely try avoid offshore bumps with combined swell for the first few sessions, as it is way harder to read and time the bumps with swell in the mix, same applies with trying proper downwinds. "Bay run"
Learn to SUP paddle in flat, then surf, then bumpy surf, then bumpy surf with rebounds, as each is a big jump in difficulty
Ideal initial conditions are bay runs, and generally finding the best combination of fetch, shelter, wind and lack of swell can be the most frustrating. 15kn stea
A swing in wind direction confuses the bumps, as does rebound from rocks and hard objects.
Logistics is a pain, 2 short runs can easily suck up 4 hours of your time with very little achieved.