very difficult to get
all the water out, i have used a couple of methods on different boards in the past, all take considerable time.
1. good for summer, stand board on its end 1 hole in bottom and 1 hole in opposite end leave in hot shed and monitor, (this can take for ever)
2. using vac pump (old fridge compressor)- connect to hole in board via a water trap of some type i.e. vegemite jar with tube from board siliconed in to the top and then another tube siliconed in to the top as well but this then connecting to the vac pump. drill hole say 3mm, in opposite end of board to allow air flow through the whole board. monitor jar so it does not overflow (or use bigger jar obviously)
3. the damp rid method was illustrated in a old issue of freesail,i havent used this method but i believe it could be usefull as another option, or used in conjunction with the vac pump method.the idea is to source a tub of damp rid (kmart)and a fish tank pump, and connect the outlet side of the pump to the board i.e silicone the tube in to hole in the board then fix to pump, then connect tube from the suction side of the fish pump into the tub of damp rid(similar to the vege jar method above)then add a hole or tube to the damprid jar somewhere in the bottom of the jar. p.s you will need another hole in the board at the opposite end to allow air(damp rid laced) to travel through the board hopefully drying out as it goes, to escape.the idea is for damprid infused air to flow through the board and exit the other end thus drying the board.
as mentioned i think combining damprid in conjunction with a vac pump may be a better solution. but fingers crossed i will never have to find out!!! and good luck,

(remember if you are pumping air in to a board make sure you have a suitably sized hole some where else other wise you will delaminate the board)