Hi Peter,
I use "old" EPO's on my boats also, until the introduction of the new EPOs nothing was as good. I am very protective of my EPOs, because I can not afford a set of those new beautiful, wonderful EPOs. Anyway, use wet/dry sandpaper all the way to 2000 or 2500grit and then polish with a buffer and polishing compound with lots of water. Testing has shown that you can not get too smooth. Try sanding a small section of you hull to 2000grit and then spray it with a water spraybottle, watch the water beads ... compare it with a section sanded only to 400grit .... The section sanded to 2000+ will not "bead" but will just run "dry" with no beading. To develope a water bead you need a surface with some slight friction to develope surface tension and produce a water bead. No friction ... no bead!