Proseal Stiffeners For Fuel Tank - N622RV Watch in HD on YouTube! Share on Facebook! Today in the shop, I started on ProSealing the fuel tank stiffeners. I found that 10 grams of ProSeal did each stiffener with just a little left over. I also found that when doing multiple stiffeners, you will use the pneumatic applicator and Van’s method of smearing the ProSeal with pop sickle sticks.