https://www.twitch.tv/hauzilla123/v/581466326 min - 5 red maps or so. It really isn't hard, the only hard thing is knowing what mods to roll on your maps.
EDIT: I didn't feel like making a new VOD so I used one from earlier this month
EDIT 2: The best way to sustain red maps is to sell other maps. While leveling past 93, you really don't want to run t8-t10's unless desirable tile setting. So why not use 2 public stash. Have one with each type of maps to sell, set note for ~b/o x chaos, have X amount. And stock the other one in another tabs. I've easily made over 30-40exa this league selling t8-t10's alone since the start. Later on, I sell t13's that I don't like for speed running.
Maps like excavation, core, abyss - low exp/bad tile setting maps.
This game's made pretty easy to solo to 100 and sustain red maps and people are still crying. It isn't hard, just adapt.
and 4 of those maps were from the zana map which had exactly ZERO packsize, no onslaught. packsize might help, but it cant guarantee red maps.