Having a higher CYA does allow you to go longer between testing and adding doses of bleach. There are several here on the forum who deliberately run a higher CYA pool for this very reason.

You can definitely add straight CYA to your pool. I usually do so myself. In a pool your size, each pound of granular CYA will increase your level by about 10ppm. There are several ways to add it. One way is to just pour it slowly into the skimmer while the pump is running and then keep your pump running about 4 or 5 days after you add it to let it dissolve in your filter. But, with a cartridge filter, that might not be the best way. You might just want to put it in an old sock and hang it in front of your return jet. Every once in awhile, give the sock a squeeze to help it dissolve faster. That is probably the best way for you to add it. (The directions on some containers actually tell you to just broadcast it across the pool, but don't do that.)