A few pointers:
- Start with each country individual AIP. There you will find permit requirements info:
AIS by State | Eurocontrol
- You're going to struggle without AFTN. How do you file your flight plans without SITA or AFTN? Most flight planning systems come with a AFTN address you can use to request permits.
- For some countries you will have to go through an agent, no way around that.
- Start building you own database of useful contacts.