RealityPaint gives you a lot of bang for the buck. Blender is a really good free alternative, but it isn't as easy to use (though you can do a lot more with it if you want, since it is a full modeling/animation software).

The big plus with RealityPaint for Poser users is it was designed to be used with Poser content. and has some great and easy to use painting and morphing tools. it comes with the texture transformer, and if you use Dawn, it is a great way to re-purpose your V4 textures for use with Dawn (other conversions are being worked on). One plus is the development of RealtyPaint has been quite active over the past couple of years, and some very nice features have been added. I have it, and have been quite happy with my investment.

All other 3d paint applications are quite a bit more both in price and complexity, and have a much greater learning curve. 3D Coat might be of interest, I think it's about $400. It might be more than what your looking for but definitely worth looking at.

I'd say download the Demo versions of both RealityPaint, 3D Coat, and any other applications of interest and try them out first to make sure they do what you want. 

Good Luck!

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