The Interlux product data sheet for 404/414 recommends only two coats
for use above the waterline, with each coat having a Dry Film Thickness
of only 2 mils. (The only bummer about 404/414 is that you need to
sand between coats...). Could it be that you're after 'high build' to
help solve fairing problems? The primer is simply meant to provide a
tie coat between faired hull and the LPU; to quote I'lux: "Use Epoxy
Barrier-Kote over clear epoxies as a sanding surfacer and to eliminate
the effects of amine blush".

So, high build is not required! If you're after high build to fill-in
some valleys... a batch of microbaloons / cabosil and a putty knife
might be better.

BTW, I'lux has a new LPU system that looks very interesting:
'Perfection'. See the video at: http://www.yachtpaint.com.

MW
Los Angeles