I've cleaned many a crevis (no pun intended) of sand, and it is easiest when dry. I've clean red sand from bellies of Hercs, and it is no fun when covered in 5606. If it is wet with water, let it dry if you can, and you normaly can clean it with a vacume and a bristle brush. If it is covered in oil and or hydraulic fluid, use an approved cleaning solvent like white spirits, to losen up the oil, and then wipe clean. Here in the middle east, most of the sand that gets into places is more like dust, and it just needs to be vacumed up and brushed out. The main problem with sand here is erosion on rotor blades and compressors.