If no one else wants to, I'll take a crack at it. There are probably a few ways to tunnel into this.
***The first thing I'd do is look at how "set up" is used by Craig in other songs. It looks like he leans on two different slang meanings (https://greensdictofslang.com/entry/ynulita):
1) 'set up' in the sense of 'prepare a disadvantaged situation for an intended target':
Set up for the slaughter and shot in the shoulder [TS&tT]
It sort of seems like one big set up [Trapper Avenue]
2) 'set up' in the sense of 'intoxicate':
Now people give me sideways looks when we set up on the strand [New Friend Jesus]
So, first, you're right that 'do drugs' is a meaning on the table, although it looks like it would have to be 'shoot up before bed' (meaning #2) rather than getting a kit ready for the morning.
***Having said that: when Craig tosses out a vague line like this in a crucial position in the song, I would bet money that there's a surprise double meaning to it. So in this case I would look for two readings, one for each of the two meanings above.
***The fact that the kids are speed shooters [SM, CiS, Smidge] accounts for part of the surprise: *they're shooting up so that they don't need to sleep.*
***There's a stretch of two weeks in both the LP and the THS stories when the kids stay on a rolling high so that they don't sleep:
two weeks maybe we should sleep [TGatSD]
He stayed up for 16 nights at a stretch, he was wrecked [TL]
It's been fifteen days but it feels like forever [SShoes]
My take (which I'm developing in some detail in the Alright Alright thread) is that the situation described in The Feelers belongs to this stretch of sleeplessness. In both stories, the two-week stretch comes before a final showdown at a big party. (For the THS story, this is the Crucifixion.) Which brings us to the second meaning; they're getting set up for the showdown, which, though it's still weeks away, is something they're going to have to get through before they can sleep again.
***Another cool thing to note about these last lines from The Feelers:
Feels like now we're in this pretty deep
We should get set up before we sleep [Feelers]
is that they echo one in A Snake In The Shower:
We dug in pretty deep and we were almost asleep
Then someone put a brick through the window [ASitS]
which is preceded by
While we've been in between places we’ve mostly been staying
At some house in the mountains her friend isn't using [ASitS]
This "house in the mountains" [ASitS] *is* "the mansion up the mountain" [Feelers]. We're talking about the same episode in the story here. And for "in between places" compare Craig's note on The Prior Procedure (link
music.apple.com/us/album/open-door-policy/1539020630):The "house in the mountains" is the place the rich guy owns.
You can chase it down further, but let me stop there. Hope that gives you something in the direction of what you were looking for ...
