As a painter (though, I don't offer painting services any more), and as someone who USES painters to paint his rank & file troops (I focus my work on commanders, tanks, etc.), I can offer a couple things.
First and foremost, insist on references. Not, "I can give you someone's email address" references, rather those references HERE on Bartertown's ITL. Granted, they may not mention quality of paint, especially if the person has only recently started offering services, but they WILL give an indication of the person's established integrity in trading. IMO, that can go a long way to support how this person will treat the transaction, and their tendency towards fair trading.
-Note to newbies; I said ESTABLISHED integrity. Please do not assume insult there.-
Another possible option is to NOT send minis. There are plenty of sites online that offer discounted minis. Some painters will buy the minis first, paint them, then you pay them when the minis are done. Typically, they want the cost of the mini's up front.... but, if you pay via paypal, you are protected.
If you do this, ensure that it is agreed that you will have the minis IN YOUR POSESSION in less than 45 days, as PayPal has a limit on how long you can wait to file a fraud report.
Can he back himself up? I am using a painter who used his presence on another site as a reference. I went there, signed up for an account, & checked him out. I verified that the email he used there was the same as the one here, I looked at his reputation there, and I verified other misc. info. It was after verifying that stuff that I decided to go ahead and ship.
Often, you will hear me say that "Enter web site here" references don't mean shite here... and they don't. My point is that it's another point of reference and verification, and THAT is always helpful.
The same goes for eBay. His feedback there will often tell you how to expect him to be. Always use the ebay "email seller" button to verify that it is the same person.
That being said; while other sites as references are good BASES for what to expect, they are NOT guarantees. Nothing is guaranteed until it is complete. Not even with established traders who have good reputations HERE.
Always keep that in mind.
So how do I handle these transactions while still being fair to the painters and not risking my stuff(and money).
Like I said. It is NEVER without risk.
I recommend using tried and true painting services.
Who are those?
The ones that come to mind (THIS IS FROM MY OWN EXPERIENCE... PAINTERS: PLEASE DO NOT BE OFFENDED IF I DO NOT LIST YOU, IT IS NO INSULT TO YOU. EITHER, I OVERLOOKED YOU, OR HAVE NOT DEALT WITH YOU):
iPAINTminis -My personal fave. Unfortunately, he is perpetually booked.
Sorcerer Studios - You PAY for it, but you get what you pay for.
Blue Table Painting - I've never used them, but they seem to REALLY have their heads on straight. If I was near them and they paid in my salary range, I'd want to go to work for them as their assembler. But, I wouldn't move there, and I'd bet the daily commute from Missouri is a real pain.
Merdain1504 & Middle Pillar Path both seem decent enough, though I have never used either, and don't know anyone who has.
Lastly, and I hate to recommend this, but it really is true... Ebay.
Go there, find some painted minis you like, then email the painter to ask if they do commissions. You can arrange it like an ebay transaction, so you both get ebay feedback, and you get a certain amount of protection. Not a HUGE amount, but some.
That's MY thoughts on it.
Eric