I feel like rub is also all about the practice and the season to taste method. I know its hard and even I forget to do it all of the time is measure EVERYTHING and take notes each cook. It makes it easier to try and replicate your successful cooks. When I cook St Louis I use a tablespoon of rub per side, baby backs half a table spoon or less. I still want to see the meat showing through but also the rub should be noticeable to the eyes. This is what works for me, but may be too much/too little for others. It also depends on the rub and what is in it. Heavy salt will get pelicle, heavy sugar need to watch it burning and turning black etc... Measure Measure Measure