Well, Mike, I'm not the best at painting either, so I fully understand not wanting to make a second attempt at it. Usually, unless my first attempt is terrible, my following attempts are worse! And I have never tried painting numbers or anything similar. It's beyond my abilities.
I'm no helicopter expert, but if you just need tail numbers then there are often decals with just numbers, letters, etc. on them, so there might be no need to have them custom made. There are also 'dry transfers', instead of the traditional water decals, and these come in numbers too.
Again, the helo experts can probably help you out best. Best of luck in your quest.
Mark