While I agree on the above method, I rarely get a boat owner that has the coin to do it this way in one shot. On New boat hulls with no previous bottom paint, a de-wax is a must as mentioned. We used Interlux 202 Solvent. I've also seen denatured alcohol used. Lots of clean rags, always changing them out so your not re-contaminating the surface.
Adhering to Manufacturers guidelines prevented us from sanding the hulls where I worked.
We used a product called Skip-Sand or No Sand Primer from Petit or Interlux. It is super thin and can be messy to apply. The Directions must be followed to the T. Period. Temperature and dry time are critical. If you cheat, the bottom paint will not adhere properly and you'll have major headaches. Seen it happen. We used Interlux A.C.T. Ablative bottom paint.
If you can afford to barrier coat the bottom first, do it. I have never done any of my boats. Same with the bottom paint. Multiple coats of a multi-season paint means you don't have to do it every season. I alter my colors every season so I know whats wearing away.
