You can buy a test kit at Home Depot. You would just take a utility knife
and cut into your paint layers at a 45 degree angle to expose enough of the
layers. Then you take a cotton swab dipped in a solution and rub the swab
on the paint. Then you touch the swab to a test strip like litmus paper,
and it turns a certain color if it contains lead. The kit is about $10.
I've found them to be pretty accurate if you follow the instructions.