The fastest easiest way I can think of would be this:
– Create a null layer and name it “CONTROLS” or whatever makes sense to you.
– Add an expression slider control to the null layer and rename it “diameter” or something like that.
– In the timeline, twirl open the CONTROLS layer to expose the diameter effects slider control and then do the same to expose one of the paint stroke layers diameter parameter.
– Alt/Option + click on the paint stroke diameter’s stopwatch to add an expression and then drag the pickwhip to the CONTROLS layer’s slider parameter and then hit Enter.
The paint stroke diameter should now be linked to the diameter slider on the CONTROLS layer with an expression like this:
thisComp.layer(“CONTROLS”).effect(“diameter”)(“Slider”)
If you right-click on the diameter property on the paint stroke layer and go to “copy expression only”, you can then paste the expression on to all of the other paint strokes so they’re all linked to the CONTROLS layer. You do have to have the brush stroke’s selected when you paste or it will just add a new stroke, which is not what you want. You need to select “Brush 1”, “Brush 2”, etc. or select the diameter property directly and then paste. The quickest way to expose them is to select all of the stroke layers and hit UU to expose all modified properties and then you can Ctrl/Cmd or Shift + click all of the Brushes to select them and then Ctrl/Cmd + V to paste the expression.
Erik Waluska
EAWmedia