M_Boats: West System barrier coat

I have my M-17 steel centerboard out and have arranged for it to be sand blasted (not with sand). I know I need to coat it almost immediately. For my boat I have used Interlux barrier coat and was going to use this for the board. But I do not have any left and you have to buy quite a bit. West System has a barrier coat additive 422 that looks like I could add to smaller batches of epoxy. Has anyone used this product? Any advice? Thanks Robbin M-17 #056