2 Rub the Vaseline onto the inside surface in a circular motion ensuring that the complete surface is covered. Be careful not to overdo the rubbing part – the idea is to get a very thin layer of oil covering the surface. Use as little as possible as the excess must be cleaned off with soft tissue paper, and the more cleaning with paper the better the chance of scratching the surface.

3 Let it stand for a while. Because of the rubbing and the heat of your fingers the Vaseline’s viscosity has dropped a little. It will work without this step but the cleaning of the surface might be overdone.

4 Wipe the inside surface with soft tissue/toilet paper or cleaned fingers, just enough that you can see clearly through the goggles or visor. Remember that it is the surface layer of Vaseline that stops the fogging so you don't want to clean it all off.

Note: If you use your fingers for the final cleaning you will see oil traces on the surface, but once the goggles/visor is on your head these traces will only be visible when you look directly into the sun. You need to use very little Vaseline, as too much will make the clearing more difficult and paper will scratch the surface.

Thanks to Joe for this great tip!