FlashSeal Elastomeric Flashing Sealant - 1 Gallon White Waterproof Sealant for Roofing, Windows & Doors - Weatherproof & Flexible Adhesive for Home & Commercial Use

I've used Flashseal to repair two leaking chimneys. It's very easy to "paint" on. If you want a nice straight edge just use some duct tape to tape off the chimney. I pretty much used a full gallon on each chimney. I'm so happy with the results that yesterday I used Flashseal to repair leaks on an enclosed trailer roof. I used the fiberglass tape and found it quite easy to cover with Flashseal.I can't speak for longevity yet but if it gets close to the 7 year guarantee I'll be very happy.