Be sure to clean the area out- make sure there aren't stray, wiry pieces of base dangling all over. Make sure your skis are room temperature, then heat/begin applying ptex. You'll be surprised at how much it takes. Apply a layer, watch it sink/settle in, then scrape off the excess. Go back and apply more, rinse/repeat/scrape until your ptex layer is flush with your bases. Apply wax liberally afterwards (let the ptex settle for at least a few hrs though).
The only good thing to come out of last winter for me in Utah with our lack of snow is I got pretty good at ptexing my skis from all the shots I kept taking. Not a pro by any means but every shot I've fixed has held and when I show my friends they for the most part can't distinguish between my bases and where I fixed them. Good news is ptex sticks cost about $1 so shots become a pretty cheap fix once you figure out how to do it.