Re: Can I sand the rest of this off....
STOP!!
A few thoughts and some sound advice..............
Bedliner IS NOT a stop leak... it may act like one but it is not the right substance to use. Aluminum boat with leaks needs to have rivets either reset or replaced, cracks welded ....... easy to find the leaks. Then use Gluvit epoxy to seal the seams and rivits from the inside. Then you can apply bedliner (waste of $$$ IMO in a small aluminum boat) or paint and add some non-slip additive if you like.
If you want to use a bedliner material for a non-slip surface you jost need to make sure there is no wax or oils on the surface. Bedliner shops use the 3m plastic scrub type wheel to clean, dull and prep the surfces for the liner. They do not strip truck beds to bare metal...... only dull the paint.
A sandblaster IS NOT a good idea for an aluminum boat. It will remove material and make things weak/thin not too mention the risk of blasting right through soft aluminum.