The simplest form of waxing a print is to rub wax into the base side until the paper becomes translucent. Plain paraffin works fine. You can get more translucency by melting the wax and working it in while hot; it will penetrate the fibers better that way, and the temperature required, about 140 F, shouldn't damage a dry emulsion (you'll routinely heat a print to higher temperature during dry mounting), but melted wax can be tricky to keep off the emulsion side of the print, and is quite difficult to remove if it gets where it doesn't belong.
(Be sure to follow appropriate safety precautions in handling melted wax -- not only can the liquid burn flesh the same way hot cooking oil can, it's also slightly flammable; it should be melted in a double boiler over an electric burner, not directly on the burner or over any kind of flame. A wax fire should be treated as a gasoline/oil type fire; DO NOT use water to extinguish, but rather smother the fire with a pot lid or similar, cover with baking soda, or use a dry chemical or CO2 extinguisher. Someone with experience making candles would be a good mentor for the melted wax method.)
If the print is sacrificial, it's much simpler to rub cooking oil into the back, but because this oil will eventually become rancid and decompose, or oxidize and harden, you shouldn't do this with a print you can't reproduce. Paraffin wax won't decompose this way, and though the print may be less archival (mostly because it will be susceptible to heat causing shifting of the wax), it's a matter of years vs. decades of life, not the weeks it will take for vegetable oil to decompose or harden.
i used single weight paper, and have never waxed heavier stuff.
