I'm in the same position too except I've a whole body and the head to paint. There are pros and cons to airbrushing and manually painting. Biggest problem with airbrushing is if you don't have one you're going to have to spend about £150+ for a decent airbrush and compressor. I've tried using air cans and they suck big time. They lose pressure very quickly and they don't last very long. There's also the problem of learning how to use one and this takes a bit of practise, they can make an almighty mess with overspray and you need to wear a respirator. However the results you get are worthwhile as you can get really tight spotting and blending of colours is easy.
Manually painting is cheaper and safer as you only need paintbrushes and sponges, but getting the tight spotting and gradual blending is possible but harder to achieve. In my experiments I've managed to get pretty good results just with a paint brush and sponge, but I was only painting a small test area. Not sure if this would translate to a larger area as acrylic paints dry very quickly and you could have problems with hard lines forming. Acrylic retardent helps but another way of aiding blending would be to use a wet on wet technique, same as Bob Ross (American Landscape artist). Mind you I'm painting on resin rather than latex.
I'm still undecided what method to use myself, so can't recommend what you should do except for trying your own experiments. If you made your own skin I'd paint some more latex onto a test area and use that to have a bash at manually painting. You might be surprised at the results. If you intend to do more work that requires airbrushing then go ahead and buy one, but if you only need the one skin painted, I'd be thinking about someone else airbrushing it or manually painting yourself. Really depends on your budget, your future intentions and your talent.
Good luck and I look forward to seeing how you get on.
