Single out an object in the compositor?

I’m completely new to the compositor, I managed (struggled) to get a blur working on a transparent background the other day and thought that was a major triumph!

I need to create a sprite for a game, this will be a space ship with some revolving parts. I need to capture xxx frames to turn into a sheet later on. All the frames will have to be transparent.

I’d like to add some lights with some slight atmospherics, usually this wouldn’t be difficult, but without a background there’s nothing for light to bounce off.

I don’t want to blur or ghost the whole object, just the lights. So, is there a way to apply composite nodes to individual meshes of an object? I can combine images later if I need to do this in separate layers.

Thanks.

In the compositor you can just select the brightest part of the image by using the Glare node’s threshold value.