I’m not sure if this what you are looking for but here’s how we solve this – personally I find the clone tool just too tedious for all but the shortest shots. Use the tracking data to move a mask around (or the layer holding the mask) then just put another copy of the video through that mask (using track matte)but shift the copy by however far you want the offset to be to have clean skin show through. These two elements sit on top of the original.
This has the advantage of you being able to keyframe the mask over time so it can better conform to the blemish and it allows you to key frame the copy over time so you can put a better “clone source” through that mask. I find doing things by hand with any of the paint tools can create some terrible “boiling” of the fix.
It also allows you to feather the mask over time for better blending.
The biggest advantage is that you can now color correct the copy and use a different transfer function for how it sits on top of the original. Many times using the colour, hue or other type of transfer function will do a better job of covering the blemish since you aren’t really covering it and then there are no matte lines to deal with.
As for using the expressions, don’t forget about the pick whip. Just add an expression to the layer’s property you want to control with data from another layer, and then drag the pick whip from the destination layer to the data layer’s property, and the expression will be written for you.