1. Remove and label all fittings and hardware that can be removed. Photograph everything before you start.
2. Scrub clean the area to be painted- the cleaner the surface the longer your sandpaper lasts and the less work you have to do.
3. Sand- You don't have to go crazy, but you do have to de-glaze the whole deck to give the surface some "ttoth" for the new paint to grip.
4. Clean- Paint won't stick to dust, dirt, crap, etc.
5. Mask off hardware that can't be removed.
6. Fill and fair any imperfections, or some of them, or most of them, depending upon your limit of perfectionism. Then raise the bar and do it all- if you don't, you will always notice that one spot you missed, overlooked or just ignored.
7. Clean again.
8. Mask off non-skid.
9. Wiht a roller and foam brush paint the non-skid with your deck paint of choice with intergrip added as per instructions. yeah, you could use kiwigrip or sand or whatever magic treatment is the flavour of the week- intergrip is $12 or so a can and is added to the paint you already have bought to paint the rest of the deck, so no compatibility issues, no extra steps, no additional prep.
10. CAREFULLY pull off masking tape surrounding non-skid before it dries. Paint deck and if desired paint another coat over non-skid zones to tone down the grittiness of intergrip.
11. Unmask hardware and reinstall removed fittings.
A gallon of paint will be plenty, (A gallon of white paint painted the topsides of a 25' wooden cruiser and the deck of Whiskeyjack), two rolls of tape will do, 2-4 rollers and a grip of foam brushes, get a box of Norton 3X sandpaper, build yourself a low-buck sandpaper cutter, use appropriate reduceds and thinners for clean up, pitch rollers and brushes rather than cleaning them, and you can have it done in a LONG hard weekend of work, for under $500.