How does Waldbühne seating work?

I know it's GA and you can sit where you want, but from looking at pictures the venue it seems to be split into three tiers.
Is there a wristband needed for the lower tiers or can you just head in late and walk up to the front?
I'd be interested to know how it works from people that have been there before.
I'd planned on heading in for white reaper around 6pm. Do you think this is too late to get a decent seat?
Thanks
Ross