When the chest hairs get more than about a quarter inch is when I wax again. Waxing over rubber wouldn't allow me to get down to the skin. Too much would be waxing legs as well as nether regions. Chafing is not an issue as long as you moisturize and protect with aloe vera immediately after. Hope this helps!
Down below? About once a month. Oh you're talking about surfboards? My bad. I use sticky bumps. Put down at least a half bar of base coat in small circles and then rail to rail. Next add the correct temp rail to rail and then nose to tail. I reapply the top coat after every other surf or as needed. Laying down a good wax job is an art and usually lasts a couple of months.