Good countries combo for 1 newbie and 1 decent player?

Title - I just got my friend into EU4 and he's struggling but he's got the itch we all have. I have 4000 hours over 12 years and he has 2 hours over 2 days. I've been a bad teacher and let him play Korea while I was Austria, then later I brought him into a 6 player friends MP game as Castile. Neither went well. I'm going to try and actually do a decent job teaching him now, but what pair of countries would be good for this?

The first I thought of was Portugal Castile, but idk if that'd be boring or not.

Any advice would be greatly appreciated! Thanks!