As mentioned above, I strip of the old wax and then re apply by heating the wax and string with a hair dryer while working it into the string with my fingers. Seems to work pretty well. Once every couple of weeks if shooting alot or in bad weather.
I also use the Scorpion venom products and have had great results. I think the SV fluid is great for getting down into the fibers and reducing friction. I also use standard Bohning wax lightly rubbed on the string to provide abrasion protection against branches etc.
I agree with this! Scorpion Venom is some of the very best string wax on the market (the polymetric bow fluid is what I use).