I wanted to make a simple constellation in a jar project as a

Masking tape?

>>922570
Yeah actually, I went for masking tape. Just seemed like too much work. :D

>>922563
Maybe mark the outside with a clear crayon like what you get in easter egg dye kits and paint over. Or layer masking tape over wax paper and make pin holes.

>>922563
If just plain circles, put masking tape on wax paper and take a hole puncher to it for easy circles. For actual star or planet shapes, decently thick kids stickers (you'll want glossy ones) will do as long as you don't overdo the paint. There should be minimal bleed if any at all.

>>922563
Seriously, that is way too much work. Just use latex based paint and knife off the parts you want to remove. It will peel off the glass easily enough. You can draw the shapes onto the paint before stenciling.

Now, when using stickers/tape, you have a lot of other problems too.