Been there and done that... lived on a van, lived on a bus, traveled the US and Europe, ran lots of sound, played bass, did the roadie thing. Alas, this was a long time ago and regional differences, Indonesia and the US are quite different, just as Europe and the US were quite different... so I'll skip things like promotion and the business side of things, other than to say...
A1. You must plan things, have back up plans, and then have a backup to your backup plan, as things can and will go wrong.
A2. The business side is mission critical, not as a means of getting rich as its highly unlikely, but that you need to have economic cushions and plans, so you don't end up hung out to dry, or worse, having to hang your audience / churches out to dry.
As far as practical, near universal things
1. Self care is key, as sometimes you won't get too sleep very much, you won't always eat well, and when working with heavy equipment, you will get injured at times. I ran a couple miles every morning, plus calisthenics. Loading / unloading trucks, buses etc only uses some muscles...being well rounded across all muscle groups is helpful. Singers I worked with said the same, they'd practice across styles, they'd take breaks, they'd try to avoid being stupid with their voice, ie, limited cheering at sporting events. Likewise learn to sleep anywhere... bus sleep is not all that great, and church pews can be incredibly comfortable, sometimes even sleeping on the floor underneath a pew for a few minutes can work wonders. (Square this up with the visiting church though, so some poor person doesn't freak out when they see a guy on the floor all of a sudden etc)
2.Self care also applies to ones own faith... I developed the habit of church crashing, ie, just because one is ministering to others every day, no matter how much you try to do on your own, you still need some form of community. I addressed this by church crashing, ie, if I had some spare time and was wondering around a given city, and saw a church sign with a service time noted, I'd crash it, even if it was vastly different than my own faith practice.
3. You need to be grounded in your faith, you will see, hear, and experience things which if unprepared for can really mess you up. The most obvious is churches preaching one thing and doing another... you might not see it so much on a local level, short of being a church insider, but when on the road, its pretty likely it will get up close and personal.
I played a huge church one night, where we raised over $70,000USD for homeless ministry. Two months later, I'm on the street busking not far from the same church, and start talking with a homeless guy. He is super distraught as he ran out of time at the Salvation Army, so they were kicking him out into subzero weather. I said, hey, I played this big concert at XYZ church, and they raised a ton of money, go see how they can help. He comes back the next day, and says XYZ says they don't do anything for the homeless, they just hosted a concert, go see the Salvation Army.
In hindsight, I should have checked the local issues / services out and had the info right at hand... and then I could have sent the homeless guy to an outfit that would truly help rather than trying to shoo the homeless guy away.
Things like the above, if rare are easy enough to work through, but they can build over time. Add in other issues like errant financial practices, sexual exploits of church staff etc, parishoner abuse, etc can rock ones faith.... More than a few Christian musicians ended up with drug and alcohol problems.
While the Ragamuffin film isn't 100% factual, many of the themes transcend time and space...
