Just use UnrealEd itself to extract the textures into something usable ...
(1) open the upl-file for the character
(2) find the value for the bodyskin (it'll be something like 'BodySkin=HitmanTextures.HitmanSkin' for the hitman-model )
(3) the first part is the name of the package ('HitmanTextures'), and since it's a texture-package that means it's extension should be 'UTX' ...
(4) start UnrealEd and select the texture-browser and open package. You should find the texture-package in the textures-directory.
(5) if you can't find the texture/package there you might want to try looking in the animations-directory as some people have stored the textures in the UKX-file for the model.
(6) you should be able to find the texture and then right-click on it to export it into a 'regular' format ...
Only problem is if the texture is compressed (= DXT1, DXT3 or DXT5-format) or if any shader/combiner has been used. In either case you can only export as DDS-format (a DirectDraw-format which AFAIK not many programs can read

). Sometimes there's a way around by finding the source-texture in that same package.
To skin a model in UPaint you'd need the PSK-file for the model ... and except for the polycount-forums I haven't seen those things in real life. You'd have to ask the author for that bit.
In fact asking the creator of the model is the best way. The people that post their models on the polycount-forums usually post an SDK (a set of files usually the 3D-model and the original bitmaps used to texture it) if they want others to help with skin.
-- edit --
I know that Juec was posted on the polycount-forums ...
here it is
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