I’ve found all sorts of techniques for lo-fi or processed sound, but here’s a few favorites—
Dropping the clock speed of fx processors. A lot Spin FV-1-based fx (and other fx) allow you to lower the clock speed of the processor–reducing the bandwidth of the processing. Makes for some great lo-fi textures. Not be confused with clocking a delay to sync with a beat. If you can input a clock to control the processor speed–I like using an osc square wave set to run the processor fairly low, and gently FMing the osc with a heavily attenuated lfo–gives a great tape warble effect.
Using a mix of a slow and fast lfo into the clock input of a delay can give some convincing wow and flutter tape effects.
Gain staging - Control of gain staging can add noise when you want it, and analog input stages can be overdriven to add texture.
Tape - Cassette 4-tracks like the Tascams are excellent for adding lo-fi sounds, and aside from the tape transfer, the EQ controls can help dialing in your flavor.
EQ and compression are fantastic tools for bringing up the noise floor, reducing bandwidth, and otherwise mangling your sound.
Attenuated and EQ’d noise into a filter cutoff can add some fine grit.