Heya cool question. We run a bitcoin focused dev shop and many of our clients pay in bitcoin.

• we setup a multi sig electrum wallet so we can manage funds together
• all our internal processes are non custodial
• we train devs in BTC. It's a mission. We also work with lots of businesses that are working on this too. Advice: make it super simple.
• process: Years of practice
• I suggest a website or app that handles both BTC and flat.
• I have a bookkeeper that is great. Not sure if I trained him in BTC or he trained me 🙂

I'll pass you his info and would love to chat if wanted. Email me at erik@velascommerce.com