I can see 3 levels:
1: camel slurry as a service. An Australian company (you get paid to cull feral camels there - extra profit) - paid for at a dedicated website - with a personalized certificate mailed for completion. Easy.
2: personalized. You travel to the machine in a suitable country and do your own camel. Bring your own needle.
3: home service - for the ultra-wealthy. Harder to do due to animal product export/import laws. Pesky laws - rich people don't need to bother about those or can find the loopholes.
You mention the theoretical tragedy of the commons problem (do you need to do your own camel, or does one machine cover all mankind?). So perhaps your buyer is an evangelical church (or believers that the bible is literal truth?). Or set up a charity.
Personally, I think if you are going to sell something as intangible as salvation, it is only ethical to sell it as many times as possible to as many people as possible! After all a salvated person has no more use for their money.