Scratch repair / sealant?

The underside of my yak is looking a little rough.  There are a lot a scratches, some are fairly deep and have plastic hanging off (obviously that part can be trimmed).  Any recommendations on what to do/use to clean up the bottom? How much would those scratches affect my speed and efficiency?

I doubt that scratches will have any measurable effect on speed/efficiency.

This stuff is great, but expensive:
http://www.westmarine.com/buy/west-system--g-flex-655-k-plastic-boat-repair-kit--9223157

Clean it real good with a scrub brush.  Let it dry completely.  Heat up a putty knife with a propane torch.  Smooth out the gouges with the hot putty knife.