I have had to do this to both my '49 & '51. I put a handfull of gravel in and shook it around real good, then took it to a radiator shop and had it boiled out. Then used the tank sealer kit from Eastwood. it comes with a metal wash and the sealer works really well. Don't try to speed drying with a fan though it will put air bubbles in the sealant. Just let it sit for at least 24 hours. If it's at least 70 deg. out it should be ok.