well im going to tackle this very thing on saturday. (05/31/08)
i dont know why it will take a "few days or so work on the front half"
from what ive read, AFTER all the prep work was done, you can do the whole tub in less than a day.
but to answer your question, i really dont see why your idea of doing in sections wont work. you MIGHT be able to see where you left off and did one half, then the other half... but if its covered by seats and such, no one will know but you.
to answer your 2nd question, no. ive had no experience with POR15. i think that if you prep that rust spot correctly, the herculiner should adhere.
also i think that the POR15 option would be much more $$ than the herculiner option.
guess it depends on what youre looking for, and how much you wanna spend
Dana 44 Front 60 Rear
TeraFlex - LCG Max Kit, SYE, 2-Low Kit, High Steer Kit w HD Tie Rod, Dual Rate S/T Sway Bar
FAB Tech Front Bumper
Poison Spider - Fenders, Roll Cage
37x12.50x17 Pro Comp Mud on 17" Pro Comp Steels
Too much more to list....