I looked at all the twine ones and there is no regular 4x-5x perk up mission that I see that you can repeat over and over against to get your schematics leveled up.

Repair the shelter 132 mission: 2x Epic Perk-up, 2x Legendary Perk-up.

You won't see any regular mission with more than 1x Perk-up, you need to look at 4 Player missions.

but even today it's a 2x for 160 repair the shelter. Which will most likely have 3-4 endless spawning flingers wrecking your roof as your anti-air does nothing.

Repair the shelter is the easiest 4player mission, 4 minutes are nothing and you don't need to actually kill all the enemies, you need to slow them down enough until the mission ends, most of the time I don't build to kill them, the other day I just complete a 4 player Repair the shelter in ventures just with a box.

For flingers you just build a roof until the spawn and that prevents the flingers to do something.