My first coat of varnish didn't dry evenly on my hull so I thought there might of been some blemishing from the epoxy that wasn't fully removed. I removed the varnish with Interlux 202 Fiberglass Solvent Wash. It did a very good job. I haven't tried it on fully cured varnish. I bought the solvent wash at a local boat shop. If you have a local boat shop near you, they could tell you if it would work on cured varnish. Good luck.