Russ - when I did Rhapsody in 2007 I ended up purchasing 4 gallons of Interprotect 2000e - 2 gal white and 2 gal grey. Overall I used about 3 gallons with a total of 4 coats rolled on alternating grey/white. Both the Petit and Interlux products are good. Good prep is the key. When it is done, let the barrier harden and if you have an inside place to work, elevated temperature is your friend to get this to harden sooner. A light hand sanding with 80 grit on a foam pad of the fully cured barrier coat will provide a nice surface to spray the desired bottom paint.