There are three types of wax that are useful to potters -- Forbes, Mobilcer A and hard paraffin wax. I don’t use or recommend paraffin because it must be heated and can easily catch fire. It also destroys your brushes. Fortunately there are two liquid waxes that are easy to use right out of the bottle. Which wax you choose depends upon the application.
Forbes is a water-based wax that has a milky, translucent quality. It's really good for waxing the bottoms of pots and rims. The brushing quality is great and it dries very quickly. Forbes can be used on greenware for single firing and bisqueware. Once dry, it has a firm non-sticky surface that resists glazes very well. Any glaze that does stick to the wax cleans up quickly with a damp sponge. If the wax is hard to see after it has dried, try adding some food coloring. Just mix a little dye right in with the wax, it will be easier to tell where wax has been applied. The color will burn out during the firing.
Mobilcer A is a solvent-free mix of wax and emulsion. Mobilcer wax is thicker and more opaque than Forbes wax. It can be thinned with a small amount of water to improve brushability. If you want to do wax resist glazing with multiple glazes, Mobilcer is the best choice. Forbes wax will not stick to an unfired glazed surface. It will peel up after a few minutes. Mobile, on the other hand, will stick to an unfired glaze and resist subsequent glaze layers. Because it is thicker than Forbes, Mobilcer wax takes a little longer to dry and stays a bit tacky. Be careful not to put the wax on excessively thick, a thin coat will do and help it dry quicker. If your wax separates during storage, shake well before using.
It is helpful to keep both types on hand so that you can do bare clay areas with Forbes and resist decoration with Mobilcer. No matter what type you are using, dedicate some brushes to wax and clean them with hot soapy water as soon as you are finished. If you are using natural hair brushes, shampoo makes a great brush cleaner. Follow with a small amount of conditioner.
Both waxes should be stored in an airtight container to keep from drying out. I pour a small amount into a yogurt container and keep the original bottle sealed tightly. Also keep in mind that is important that neither wax ever freezes. They become an unruly mass of goo that will never go back into solution.