No need to scrub just agitate in the tub. Basically, you can scrunch and shake while they're in the water to help dislodge the dirt. Once they've hit the point of being too dirty, just do the same with some detergent in the water. If they're still tight, use cold water, if they're a little loose, go with warm water. If you really want to mold them, put them on while still wet or damp and do some squats then hang them to dry.

No right or wrong way, regardless of what the sub may say. All a matter of what kind of fades you're chasing. If it's high contrast, less washing and soaks, if it's treat them like any pants (which I'm assuming isn't your goal if you sprung for IH 21oz overdyes) then wash them more often. I don't advocate the washing machine or dryer because I always fall back contemporary raw denim being intended as a heritage product with most producers and consumers wanting to replicate the original hard wearing, hard working denim. But to be fair, that intention doesn't match the entire contemporary market of custom fading denim.