: It's just generic multipurpose stuff (not garnet though, which I think I
: heard is quite soft), 120 grit. It doesn't tell me what material the
: abrasive is made out of.

Start with a much coarser grit. Probably try 55 or 65, or extra coarse. It will take off the big drips faster, and the spaces between the grit are larger and take longer to clog up. This will leave a regular pattern of rather even scratchmarks. Then switch to a finer grit -- maybe something around 80 to remove the scratches, and only then go for the 100 to 120 to smooth things over.

Until you are working with the last couple coats of varnish you don't need to go much finer than 100 grit. Any visible scratches left by that are going to get filled in by the next application of resin or finish, and those deeper areas are sometimes desireable for better bonding between layers of resin and/or varnish.

Sanding is more than a task, it is a philosophy. Learn to enjoy the social aspects of sanding by buying 6 paks of cold beverages and inviting friends to lend a hand. Or, appreciate the solitude as you lose your inner being into the whine of the sander while you meditate on the patterns formed on the surface of your boat.

hope this helps.

PGJ