See the page in:
1. Remove old paint and dry the wood. Clear Penetrating Epoxy Sealer (C.P.E.S.)™ will not work properly if the wood is waterlogged, and will not soak through old paint.
2. Clean off the loose, crumbly, rotten wood. C.P.E.S. works best on wood that cannot be easily picked off.
3. Saturate the wood with C.P.E.S. The filler (Fill-It Epoxy Filler) sticks better to wood treated first with the sealer.
4. After the solvents have evaporated (a day to a week, depending on ventilation and depth of decay), apply the filler.
5. The next day the Filler may be sanded to shape.
6. Before painting, apply one more coat of C.P.E.S. to help the paint bond better to the wood and filler.