Frank,

I'd try the rinse/backwash rotation a few times before bringing it back to filter.

Rinse
Backwash
Rinse
Backwash
Rinse
Backwash
then finally filter.

(shutting the pump off in between the turning of the valve handle each time, that your doing correctly).

But that's more a remedy for high pressure, then anything else, which you are not experiencing.

Nothing but the highest of pressures should cause sand to get back through and into the pool. The filter itself is designed to not let sand through, so you could have something wrong with it mechanically. It could have been installed improperly and you just starting to see the effects of that now.