Yep, I have thick hair and it’s really long, past my waist, so I know the suffering with knots. I have always been told that my hair is in lovely condition though especially considering it’s length and thickness, so a couple of things I always do,
Brush my hair before I wash it, saves getting it in the water or down the drain, just in case though, get one of those little sink hole cages that catch stuff.
When conditioning my hair, I use quite a bit and rather than massage it in in circles, I tip my head upside down and then apply it scalp to tips in a straight motion, once my hair has a decent covering, I then make sure to rub it in well, still refraining from using any rubbing in circles or messy moves. Then leave on for a good 5 minutes.
Wash out the conditioner and then again, I tip my head upside down and wrap a towel around my hair and rubbing the back off my skull first then wrapping the towel around my hair and rubbing it between my hands (sort of like spinning how you would a twig to start a fire motion) but gently and keep going root to tip, this will prevent tangles.
Once that is done I use a good quality Argan Oil spray, give a fine and gentle mist over my hair and that not only leaves a nice shine when dry, but it also helps give good condition and prevent knots.
Then sectioning my hair into two sides, like pigtails, straight down the back and over each shoulder, then using a detangling brush (cheap to buy FYI, and less painful when you have tangles!) brush gently from the ends then working further up the hair, only doing a little at a time, working higher and on each side, once both sides are tangle free, dry pointing the hairdryer straight down DO NOT swoosh it side to side a lot etc, that will blow the hair everywhere and cause tangles.
Hope it helps!