You need super armor unit in front Hashirama,so he can't start combo and steal your chakra.Also,if you have any ninjas that dodge chase,will help too.

Super armor ninjas-Gaara,angel Konan,samehada Kisame,Ginkaku with BT,Kakuzu.Or you c*e earth main,he have super armor skill.

Ninjas dodging chase-taisho Konan,edo Itachi,5k Madara,GNW Madara,susanoo Kakashi.

I beat 300 on first try with Kakuzu,edo Itachi,taisho Konan,fire main,160k power.First round is a joke.Second,if they don't start combo,and absorb your chakra,they don't use mystery,so just need to survive their standard attacks.