two methods ive found restore it to good new condition.
I like to use Lysol disinfecting wipes to saturate it and lay it on a hard surface turn the mouse scroll ball down facing the surface top/lysol wipe.
do the 360 and then do slide it one way continuously then the other way, etc horizonally to the right repeatedly then to the left.
then you can use that same wipe, when its dried, to dry off the mouse and should work wonderfully.
the problem with the 360 method it just rotates all the particles around inside there. so it doesnt do an efficient job.
2) and another method i like, is using a typical Twist Tye flatten it out as much as you can place it in between the scrollball and the edge and work your way all the way around as it will unclog most of everything in there and pikc up stuff deep that cant be wiped out.
hope that helps