Thanks, Loretia! I made a new a batch with Krylon Make It Last sealer. Same as you - started with a couple of very light coats and then added a couple more on top just to be sure. They seem to be holding up fine.
When I'm finished with this can I'll check out the Americana brand. I purchased mine at Hobby Lobby for $5.99 (then used a 40% off coupon, of course!).