This is totally fun and messy at the same time.
You will need at least one large can of wax and maybe even part of a second can.
Lay out some newspapers and lay the coat flat on the floor. Smear some wax on your hands and then start crudely laying the wax down on the coat. Pay special attention to the top of the shoullders and the arms, seams and pockets.
Lay out wax until the coat seems to have wax stripes on the whole surface. You need not get every square inch covered but you want a generous supply of wax over as much of the coat as you can.
Then snap/zip/button it up and turn it inside out completely. Put it in the dryer on a warm setting for about 10 minutes. This is the secret...this distrubutes the wax even though you did not get it on perfectly uniform.
Pull it out of the dryer and open it up and inspect it for any dry spots. Hit those spots again and repeat the dry for a couple of minutes.
Applying the wax in the hot sun also works but I much prefer the dryer method.
I wax my coats yearly but after 3 years yours will be very dry so make sure you have enough wax before you start. The light 6oz may not need a full can but my tin and shelter coats take more than a tin if they are dry.
Good luck, and never never tell your significant other what you were doing to the dryer <img src="/images/graemlins/shocked.gif" alt="" />
Actually the wax tends to stay inside my coats when I abuse the dryer like this....but waterproof towels are an interesting thing too.
This is my shelter cloth Packer that I generously waxed just before my trip to SE Alaska this spring. If you have a double layer like this coat make sure you hit the inside layer too.