YOU CAN USE MEK HARDENER. THE STUFF THATS USED WHEN YOU FIBERGLASS,, POLYESTER HARDENER..MIX IT IN GOOD.. HARD TO SEE IF ITS MIXIED.. LESS GIVES YOU MORE TIME .A BOUT 3 DROPS TO A GOLF BALL SIZE GLOB OF BONDO.. DO A FEW TEST GLOBS FIRST.. 1 DROP WILL STILL GET HARD.. OLD FIBERGLASS TRICK..FOR FILLETS.. LETS THE FILLET AND GLASS SET UP AT THE SAME RATE.. NO SHRINKAGE..