[Red62]

This is what you do:
1. Go to a clean place with clean towel on a table
2. Take a cup of water. Dip the end of the magazine into said water and try to shake off as much sand as you can.
3. Take a screw driver and take out the valve. Be sure to depressurize the mag before doing so.
4: The valve will have two sections that are screwed together. With a needle nose pliers, gently take apart the valve.
5: You will find a spring inside. Putting that aside with the cap, use the back of a small drill bit to punch out the probe.
6: remove rubber ring on probe. This piece is very sensitive: do not get dirty
7: take a water bottle half filled with water
8: take probe, put into bottle, close the cap and shake till your heart's content.
9: strain bottle to retrieve probe. Coffee filters would catch the sand too: don't want that, but you can strain into a filter in case the probe falls through the strainer (I doubt it will happen)
10: reassemble valve and reinsert into magazine
11: give it a test.
If test fails:
O1: take probe back out
O2: use pliers to hold probe by the stem
O3: use duster to try to blow from the back end to try clearing the intake port.

Do not get rings dirty
Do not use loose strain towel: you'll lose your o-ring.
If you still can't seem to get it out, you could always buy a new valve for maybe $5? maybe.