Don’t do it. Those seals grip to the edge and require no sealer. Sealer is for seals that rest on the surface. A fresh factory seal will do the trick, but I doubt that’s where the water is getting in. Depending on the year, neons are known for leaking around the taillights and through cracks in the body seams. Pull the carpet, drop the back seat, lay in there with a flashlight, close the lid and have a friend hit the car with a water hose. Shoot the taillights and around the undersides and wheel wells where the seams meet. I bet you’ll find a leak.