Last year I was repairing and refinishing a fiberglass Sunfish and was using Interlux paints. The paint was brushing on too stiffly and so I ran out to buy some Interlux 333 Brushing Liquid (at $17/pint at the local West Marine!!!). It worked fine, though it really frosted me to pay that much. Later in the season I needed to paint another boat and varnish a kayak I built. Just for giggles, I looked up the MSDS for the 333 Brushing Liquid and found that it is: "50%-75% Kerosene and 50%-75% Solvent Naptha" There is no other mention of other dryers or ingredients. Now, my math ain't what it once was but it seems to me that a formula that is >/= 50% of component A and >/= 50% of component B is a 50-50 mix! So I mixed up some equal parts of kerosene (@ $4/gallon) and Naptha (@ $20/gallon) and made my own at the cost of $3/pint vs. $17. I tried it with both paint and varnish on some test boards and it worked just like the real stuff, application was easy and it dried free of brush marks.