oskar speaks truth.
i played 7k hands at 5nl last month on the comeback. Win rate was pretty silly, maybe sustainable, maybe not.

some things to add.

You can just play loads of pots vs the loose whale-fish, take down heaps of small pots vs the nits, 3b buttons vs mp/lp ranges with blockers all day, don't play big pots vs a raise from the nits without the nuts, steal a ridiculous amount, not get much better at poker, and move up to 10nl in a few hours. Oh, and never bother to waitlist. Just help start tables. Sit opposite any player you think is reg, or just wait then jesus-seat cos who cares re etiquette at 5nl, it's not like you're planning on staying there for long.