Wear old clothes (might want to have latex gloves on hand) and put down an old sheet or something. I've found that wax gets everywhere & it's near impossible to get out from under your nails.
When I reproofed my Barbour, I cut up a rag and used a small piece to kind of massage the wax into the fabric. Once the entire coat was waxed, I hung it up & used a hairdryer on low/med heat (hold it about 8-10" away from the coat) to slightly melt the wax into the fibers. Worked great, still going strong 8 years later!
I would advise reproofing the entire coat at once - it is a bit of a PITA to do and you might as well get it over with in one shot!
There will be instructions on the jar, but:
Make sure coat is clean to start with (hose off if you have to) and dry. Heat jar (hubby found 10 seconds in microwave is perfect, or put jar in hot water) to melt wax. Paint on with a brush or rag. Allow to dry in warm, dry area.
Probably do it outside if the weather's nice or you'll smell the wax for a long time. And, yeah, maybe bite the bullet and spend the time to do the whole thing at once. If part of it's going, the rest will soon anyway.
"Radar, the man's ex-cavalry: if he sees four flies having a meeting, he knows they're talking about a horse!" Cptn. BJ Hunnicutt, M*A*S*H Season 4, Episode "Dear Mildred"
How timely! My Outback Trading Company oilskin jacket was peed on by a barn dog so I blindly tossed it in the wash and then the dryer. Needless to say it came out 100% not waterproofed and I thought I had ruined it for good. Viney did you order the wax through Outback?