Paint tool value sampling
For painting mesh colors and skin weights: Allow user to hold a hotkey down that puts the paint tool into a sample mode. When user LMB on the surface the paint tool samples geometry within the tool radius and averages values into a single RGBA or skin weight value - and uses that value to set the current paint tool value. This allows user in the case of skinweight editing to sample a vertex - then modify the current value up/down using N+LMB - then paint a new value on the vertex. Same deal on the RGBA side - sample - tweak - re-apply.