Hi! I am pretty sure that I 've seen some video (probably here) where someone showed different masking techniques using a brush (no Transpose tool) and the areas were masked based on the topology (angle, flat surface aso)… i think? Don’t think polygroups were used either… but I am not sure. 
I want to mask out the flat part of the cutted wrist, with clean edges. Is it possible to do that using some technique like this?
Hope someone can help. Thanks!
/ Frederik
Use the TransposeSmartMask brush but make sure the Brush Modifier slider is set to 100 in Brush>Modifiers. Hold Ctrl and drag on surface.
Thanks zber2. TransposeSmartMask worked fine for the wrist, thanks. But just so that I know, are there any brushes that can be set to only affect certain surfaces or angles also? Maybe a setting that affect all brushes? I think the video I refer to showed how a Trim brush was used to clean up (or create) some hard edges, and this “filter/mask/setting” made it very easy to do this without destroying surrounding areas… any ideas?
I think you might be referring to the MAHMask Bias custom brush from Mahlikus The Black. If it’s not that then I don’t know of any other. Sorry.