My problem with low residue is that it steers people into a state of fear of fiber while I believe fiber is integral to balancing the SCFA producing bacteria in the colon and reducing diarrhea.
After much research I pursued this route and it worked for me, I'm diarrhea free for 2+ months now.
I started off with safe fibers from powdered, prebiotic supplements like inulin, FOS, psyllium, polydextrose etc. You can research resistant fiber online and find powdered supplements with these in most health food stores.
Along with this safflower oil is know to be good for rebalancing the gut flora into one favoring non-diarrhea bowel habits.
Until you see a reduction in diarrhea you should avoid simple sugars, prioritizing high fructose corn syrup as well as sugar alcohols like sorbitol, xylitol, etc. and sucralose, the fake sugar, which is linked to death of healthy gut bacteria. Also avoid maltodextrin and emulsifiers like polysorbate whenever possible. If you need sugar like in your coffee pick up stevia. Bonus points if it has inulin in it.
Probiotics may help but mileage may vary, get S. Bouliardi if anything, but our aim is to restore the natural gut bacteria. Adding in non-native ones will only help so long as you continue to take them, and that's usually cost prohibitive.
When you start feeling better you can consider certain raw fruits and veggies, I would stick to low sugar ones. Carrots are loaded with vit A which is great for crohn's. Bananas have FOS, a prebiotic fiber, and potassium, though high in sugar, still a good choice. Strawberries are deceptively low in sugar for how sweet they are and high in Vit C, always get organic to avoid pesticides!
Sauerkraut is another great choice. If you can buy it organic at a healthfood store with only cabbage and salt on the ingredients label, go for it, if not buy a cabbage and a jar and make your own.
You'll want to gradually introduce a stream of foods containing easy to digest fibers to maintain fiber intake throughout the day. Look for rice-based foods. I would suggest looking into gluten-free baked products, some sugar is okay in these as the fibers will help to offset it.
This is a long process, do not expect instant relief. If you get worsening of symptoms, stop what you're doing, re-evaluate, take less fiber. At no point should you feel worse, I don't believe this should cause 'herxing' or die-off.