The sand paper inserts are only partially effective at keeping the tips of the nails blunt. You will most likely need to trim them once in a while anyway.
If you have not taken your glider for a well check up with a glider experienced vet - that is recommended for any glider new to your home to make sure the glider is healthy. The vet will also do fecal testing to make sure there are no parasite issues that need to be treated. You can also have the vet cut the nails for you the first time and show you how to do it.
After the nails are cut, the sandpaper inserts may extend the time between trims.
Once your glider is used to your hands and being handled, nail trimming will get much easier.