Ok - best advice I can offer. ensure you go for a light base coat in a distinct colour - (none fleshy) probably blue would suit (use this as an example - red goes too fleshy, blacks/grey/ yellow no distiction - green could work though as could white)! -
Black line the edges of the shorts and dark wash any fleshy bits you want to point out (such as his bitz!!) to ensure they for the detail on the shorts use a little darker blues rather than black as this won't spoil the effect, do a couple of pockets in the old
- - - - patern and a few belt rings // // //. if dwarf has any muscles you are washing follow the same ridges on the shorts but in blue.
a few highlights on shorts to distiguish washed areas (especially on his Bitz!) and to ensure it is clear - you may want to run a scar design from his leg and onto his tattoo -;-;-;-;-;- like!.
difficult job - keep his flesh mostly clear with only the odd tatoo (possibly in same colours so that the focus is his shorts. Hope this helps!!
