Hi Alistair,when i varnished my plank bowsprit last year and old salt told me to sand back to bare wood,then mix the first coat of varnish with turps about 50 50,so it soaks right in,then leave for 24 hours and lightly sand,then apply another 50 50 coat,do this for 3 coats and then 4 coats of pure varnish,take care to leave at least 24hrs between coats and lightly sand between coats,result mirror finish.no doubt someone will come on here later with a different method but this worked for me. dont bother to anti foul as it will be in and out quite often.