I have seen a lot of questions about making trails recently, so I thought I would see what I could come up with...
I tried two different ways - the first way (the "fake" way) was to use a single sprite that uses gradient to fade the trail out. It works well, and has no performance trouble. But it can't change shape - so it wont follow an object randomly around the screen. I have two balls moving around a circle and the trails follow the balls around the circle, but that is all they can do.
The other approach is to use a lot of objects to build a trail and have them fade out and shrink down in size as they fade. This allows for a real trail that can follow an object. You can control how fast the trail fades out, how closely positioned the objects are to make the trail look solid, etc...
https://www.rieperts.com/games/forum/Trails.capx