Ian, I know just how you feel. I can utterly ruin a perfectly acceptable model with one of my appalling paint jobs! I cheat somewhat though. I choose a model which even I can paint. I recently finished, well, nearly, a Fairmile MTB. I hand painted it as I guessed the original would have been hand painted. If the original was hand painted, then some of the lines would not have been perfect, there would be the odd run or two etc: perfect for my 'skill', as it were. The result, I think, was quite good. Last summer, a chap (ex RN) chatting to me mentioned that a weekend 'jankers' was to paint the bridge...with a 1" brush! I doubt anyone doing that would have taken an awful lot of time to get everything perfect! So, if you're doing a working boat, the paint job won't necessarily be perfect. If it's a rather posh boat, then...get someone else to do it!
Mike