This is one of those things where you wonder why you hadn't figured it out years ago. Here I was trying to use plain old egg wash to make stuff stick to other food stuffs when I should have been using whipped egg whites! No more delicious coatings falling off into the pan!
Whip an egg white to a soft peak. Pat dry and season whatever it is you're coating (in this case a salmon fillet). Dip in the egg white and then press into the coating mixture (in this case sesame seeds but finely chopped nuts worked great too). Place encrusted side down in a medium hot oiled pan until browned. Then flip and finish on the stove top or in a hot oven.