I assembled a rough facsimile of a Weirding Module out of a chain of cheap Chinese pedals that I already had. A VSN octave into a Mosky phaser into a Behringer fuzz into a Flamma envelope. It's not exactly the same but it's close enough to be a lot of fun.

I wouldn't know where to start with a rainbow machine, though. Those are pretty thoroughly unique.

Yep, definitely take stock of what you have -- it sounds like you have a pretty extensive set of effects already, and all a tube distortion box is going to get you is another preamp/drive pedal. (Are you using a Kemper or HX Stomp or something?) If you're going to tone-chase, it's probably helpful to lay out some concrete goals for what you're trying to do, and then figure out what, if anything, is missing from your setup. In my case, it was that I didn't like either of my amps and I was trying to get a more aggressive metal rhythm sound. I was hoping that could transform my extremely clean-sounding Fender combo into something in the same ballpark as a Krankenstein or a 5150. It didn't, and it turns out that my other amp was capable of those sounds all along with just a Tube Screamer clone, a better speaker cabinet, and replacing a dying preamp tube.

If you get stumped trying to dial in what you have, it can be pretty helpful to go over YouTube demos to see how other people are using the same pieces of gear. That will at least give you a frame of reference. For me, some of Kyle Bull's videos have been pretty enlightening -- the dude is a wizard at dialing in high-gain thrash metal sounds, and he's one of the only gear nerds I've seen who makes sure to always use the same cabinet, speaker, and mic combination for his demos' audio tracks. That's honestly pretty helpful, especially if you have access to a Two Notes Captor or are running through VSTs for your amp sound.