[pelican]

let me add this:

working with plywood:
it's real important to seal the wood from any water migration - epoxy is the clear choice for this...and yes,you want to completley seal the edges of any and all plywood - it wicks moisture via the end grain...epoxy is a better choice for working with wood,due to the fact it's water proof - polyester resins are pourous,not the best choice for working with wood.
the underside of the wood - you need to seal this as well...

spraying with gel coat:

gel coat requires a few steps - surface prep,spraying - 2 types of gel coat - "laminating gel" - this will not fully kick,unless sealed from the atmosphere with PVA.and there's "air dry gel" this has a wax in it that rises as the gel kicks - no need for PVA - the gel needs to be sprayed on to the needed thickness - gel shrinks...after the spraying,wet sanding and compounding is required...
in the case of decks - the gel is rolled out...

depending on what you want - a nice clean job,or a "utilitarian" job - that meaning,you're not really concerned with beauty - gel coat may or may not be your best choice...

finish coating with awlgrip is gonna give you a nice clean finish,that lasts,awlgrip on the deck is clean and easy to keep that way.refinishing with paint,you need the prep,a good 2 part primer and then spray it - job over...
rolling out the non skid areas...


seriously - check out composites,before you start this job - composites are pretty easy to work with,light weight and strong as well...cost is less than you think - 1/2" penske board 4'x8',costs around $150...