Maybe he'll do lots of those Force shove things. Plus, OB1 isn't dueling the whole time. It's Anakin vs. Dooku. Then Dooku enrages Anakin by telling him he killed Padme and that it was OB1's fault. Anakin then turns on OB1 and Yoda enters the scene. Dooku gets worked but escapes, Anakin gets knocked out by the crane and OB1 gets injured, and Yoda gets worn out.
This should be a very, VERY interesting duel. Especially because Yoda finally takes a STAB at dueling on the silver screen.
Same way any master swordsman fights two opponents- good movement and position.
Swordfighting is a real life thing you know!
And, incidentally, how come you don't ask how Darth Maul can fight two people at once? A double-bladed sabre does not make it any easier, you know! Once you block with one half the other is useless.