No need remove heat-sink for simple cleaning GPU, you can use paint brush and compressed canned air.
A soft bristle pain brush for dusting is perfectly safe. Or a small paint brush for watercolor for the tiny spots. I am using such brushes for 15 years and my father for even longer, never ever had any problem.. You can purchase a soft brush from almoust any convinience store. With air in a can, you can't remove the dust that sticks to matte surfaces - like fans, case surface, non glossy finish PCBs or metal heatsinks. Using a brush requires extra attention. Do not use force when brushing off the dust. Do not brush things like the CPU socket for example. Do not use hard brushes or brushes with metallic bristles. Soft (prefferably...