Hi David, Rub them down a bit at corners and a few other places that might had had wear then use antique wax to seal them when you are happy.
Use antiquing wax found in craft stores next to the chalk paint. Rub TINY amounts into the crevices and wipe off immediately. Buff.
You can also dry brush a “dirty white” paint or stain on them.
I've been told by several paint specialists that latex paint will not hold the staining waxes! I'm sure that is the case with oil base paint as well. Check with a professional before trying that