Create a block sanding guide-coat by covering with a contrasting color.

Block Sanding reveals high spots and pin holes.

Using a pencil, mark each pin hole immediately, the second you see it!  Those little things get lost in a hurry only to be found after the clear coat is on.

After the plug is completely free of any defects by block sanding with 400-grit wet, machine buff the plug using TR311 liquid compound

Then, machine buff with TR301 sealer glaze. (using a different bonnet.)

Then, apply 5 coats of mold release wax.  This is the kind of stuff you cannot let dry.  It is designed to be wiped off within 15 minutes of application.  Do not do it too soon either.  It should take a little elbow grease to get it off otherwise penetration may not occur completely.  Wait at least 6 hours between coats.

The final step before shooting the gelcoat is to shoot a coat of PVA (poly vinyl alcohol).  I have had great success with the water-based partall.  It is a tricky material to spray because it easily runs.

Using a cup gun, apply a firm coat of gelcoat to the plug.

The rim around the bottom of the plug is a flange made out of modeling clay.  This was in place before the application of the PVA, however, I did not take any pictures.  This flange creates a nice edge that aids the fabrication of the final parts.

Gelcoat takes about 4-6 hours to firm up.

Once the gelcoat has firmed up but is still tacky, begin reinforcing the mold with fiberglass.  Focus initially on the edges, but don't neglect the flat sections as any non-reinforced areas will develop a hole.

Continue until the entire mold is covered with fiberglass reinforcement.  Let the Fiberglass cure overnight.

Flip the mold over and release the mold from the plug using plastic wedges and jets of air.  Keep working it gently and eventually the mold will release from the plug.

The PVA just peels right off.  Wash the mold completely with soapy water.  The PVA is water soluble and this will clean the reamaining traces.

Create a box to reinforce the mold while working with it to prevent damage to the mold.