Hey Luke, I haven't used an Intellifex but the basics of what they do is the same as other multi effect units. So the majority of the effects are time based, chorus is very short delay and modulate the delayed signal, delay is delay, and reverb is lots and lots of different delays (reflections).
With both delay and reverb times you can set them to the speed of the song, some units have a Tap feature so you can tap along with the song and set the delay time. Or work out the speed in beets per second and then decide your delay time (1/4 beat, half beat etc). Some where between 250ms and 300 ms is usable short(ish) delay time, go for longer for the big echo's (depends how/what you are playing), adjust the feedback for how many repeats you want. Of course there's lots of delay types, I generally use a stereo L 250ms R 300ms not much feedback and mixed quite back (as is on my rhythm sound). If you want the longest delays they will be mono as stereo takes more resources etc..
For reverb (and I have reverb on all sounds), you can get pedantic (like when your recording) and make sure the reverb time is a product of the song speed e.g. 2.5 seconds. There are also lots of reverb variables to emulate many different spaces. On guitar I usually go for a small room and turn the low and hi pass filters off, a little pre-delay. Plate reverb is good for percussive stuff, I use it on drums.
Cheers R