A lot of this is BS. Having one bowel movement per 72 hours is everything BUT normal. We as humans are meant to eat plenty of fibre (from fruit and vegetables) just like the apes we descend from.

You have good fibre and bad fibre... too few fibre and too much fibre.

For colon cleansing... psyllium and flax seed fibre are very good and gentle to the intestines (especially flax, or psyllium combined with flax), because of the mucilage it creates and the water it absorbs. It makes your stool softer because it absorbs a lot of water.
Fruit and vegetable fibres are also gentle, and they promote good bowel flora.

Wheat bran for example does not have this mucilage, and indeed can damage the colon lining (when ingested in large amounts). It can also aggravate constipation because it dehydrates the stool even more.

When you are constipated, first take some mild herbal laxative (e.g. cascara sagrada... not senna) for a week, and drink plenty of water.
Then when the 'big load' is out... start with psyllium/flax fibre (start slowly, increase amount of fibre gradually), consuming plenty of water/juices ALONG with using the herbal laxative to keep things moving. Do this for two weeks, then take a one week break, in which you use a good probiotic and continue drinking lots of fluids. You can then start again with the fibre and herbal laxative (for max. 3 weeks, then take a break again)

This is an effective way to cleanse the colon.

Afterwards keep your colon healthy by eating lots of vegetables and some fruit, preferably 50% raw.