[Greg Gesch]

Hi. Sorry can’t help with your actual question, however if you want to add a stroke to the combined shape you could select your layer and then try Layer Styles/Stroke.

[Greg Gesch]

Hi, someone had exactly the same question, and got an answer, here:
https://forums.adobe.com/message/10920109#10920109

[Greg Gesch]

Hi Esther, have you looked at the Cartoon effect (it has line thickness controls)?

[Greg Gesch]

Hi. Have you accidentally changed the Local/World Axis buttons at the top of your screen?

[Greg Gesch]

Hi. You might find this useful:
https://www.videocopilot.net/tutorials/realistic_rain_drop_fx/

[Greg Gesch]

Hi. Here’s how:
https://forums.adobe.com/thread/2528069
It goes onto two pages the second has a video and variation of the method.

[Greg Gesch]

Hi, turn the Fill of your shape off.

[Greg Gesch]

Hi, you could try precomposing two versions (1 going up, 1 going down). Mask out and subtract the still columns in your main comp, and then offset the X position of the one that needs the fewer rows(?).

[Greg Gesch]

Hi. Does it still happen if the Brush Positions aren’t pickwhipped?

[Greg Gesch]

Hi. Try increasing your Mesh Expansion (sometimes it leaves bits behind).