I use a stainless steel filter with a 100 micron mesh. It drops right into the mason jar for steeping. When it’s ready, I pull out the filter, dump the grounds, rinse it out, and start the next batch. I’ve seen filters with more fine or course meshes, but I find the 100 micron to be good for course-ground coffee, like is typically recommended for a french press.
Personally I do not make concentrate. I use a smaller amount of grounds to make ready-to-drink cold brew. But you can do it either way.