XRAY - Model racing cars

Hey guys,
I race my XII on asphalt and its pretty dusty. I find that if I dont replace the grease in my damper disc the car is like eratic on my next run...
I use the standard xray diff grease and some shock oil 350 or 450cst.
After my 8minutes run its like nothing left in the damper disk...
How often do you grease yours.? And is it and alternative for the diff grease.
How much do you put in?
I tried different grease but cant get one as thin and soft as the Xray diff grease, with thicker grease my rear pod doesnt reach the same.
Any help will be much appreciated.
Thanks