how do i do it?

The only way to be 100% sure you don't get any sand in your engine is to not run it in sand. Other than that just make sure you have a good 2 stage airfilter secured with a ziptie, always flush out the top of your head with fuel or alcohol before you pull your glo plug, and keep as much excess oil as you can drained out of your pipe.

Do you think the stock t-maxx 2.5 filter would do a good job? Any recommendations on other filters good at this? I'm also thinking about taking my nitro to the beach. What else should i do?

On the beach your stock filter should do fine. It's the fine dust that gets by filters and their ain't none at the beach. The big killer with sand is it works into the moving parts like A arm pivot holes, bearings, etc.

then ill use one of thoose compresed air spray can things to shoot out the sand...

Using compressed air will only drive it deeper into the places you don't want it to be. The only fix is to strip it down when you are done and clean it all out.