-Deply 1 Fedaykin next to opponent's base to call a worm..

-Put the rest of the fremen in the trench and put them on gaurd mode.

-When worm comes, chase enemy harvestors toward the trench and have the fedaykin attack the harvestors.

-Undobtedly, you opponent's units will come to the situation to rescue the harvesters. Goble the units up and have your fremen take care of the rest. (Fedaykin vs Tanks & Warriors will shoot down infantry.)