Whenever I've cleaned my SI, I use the trigger nozzle on the garden hose to really blast out any junk, opening and closing it a few times, then spray with WD-40 to clear out any water, then towel dry and apply whatever oil I've got (usually some CLP).
Only time I've gotten any grit in a SAK, it was some metal filings from sharpening my sidelock Adventurer that dribbled down the blade (I was using a carbide oilstone) and into the hinge. That took a lot of shoving the WD-40 nozzle into the joint to spray it out as best as possible, but some grit wouldn't dislodge right away. I kept it as well oiled as I could, it eventually worked itself out.
Matt in Texas