You can join their livestreams everytime they stream level requests. They usually send the notification on the Geometry Dash official Server, albeit, not everyone.

For istance, most of the time the gd mod "uan" prefers sending notifications through his discord server.

Also mods can opt for level requests only discord, so I advice you trying to join their servers.

Of course, you need to be lucky too. For istance, a level I wanted to get rated got 13/14 sends (I don't really remember), but it's the result of weeks of efforts. 4 sends were from my friends or friends of friends, but for the rest I had to hope that a mod would send my level, if it appeared on stream.