I took the view that rivets would have three points of sealing; one on the head, one on the shop end and between the rib and skin. Sealant was applied using either a Popsicle stick or syringe. I started mixing three batches, putting two in the freezer and using one. But, the freezer sealant was less easy to use being rather cold and stiff. Eventually, batches of 100 oz were used, this equates to one ribs worth. Everything was regularly cleaned with acetone during the riveting, this kept sealant from going everywhere and helped stop tools sliding during riveting. The inside of the ribs where cleaned prior to sealing the shop head; I was anxious that small pieces of sealant might come adrift in the tank and go down fuel lines.
Take Away Coffee Shops have wonderful small Popsicle sticks for stirring coffee, these are perfect for making seals along the ribs.