Fur should be full, soft, & free of mites, & other bugs. Be sure that there is no sign of hair loss in any area other than the chest scent gland & the one on the head.(of males.)
The scent gland is generally clean, althought when scared, mating, or marking they may get gooey & or have a faint smell.
There isn’t much need to brush them, but if needed you can use a baby wipe or wash cloth to to clean them.
Gliders fur is pretty soft, close to a chinchilla, but not quite.