My 2 DD's have mixed race corkscrews. I've tried everything over the last 4 or so years - here are my pearls of wisdom:
Avoid 'cones' - silicones etc. Feel good, but ultimately lead to more problems.
Boots NAKED range (mentioned above) is the best I've found for the price. There are very expensive products which might be good but I can't afford them. NAKED range is often on 3 for 2 offers. If your local Boots doesn't stock NAKED products you can buy online and get it delivered for free to your local branch.
I wash hair once a week and brush it through with the conditioner on to get all the knots out. As good as the NAKED curl conditioner is, I have recently taken to using Aussie 3 minute rescue as a conditioner - to get the knots out. It makes a huge difference.
I use a blend of pure argan oil and macademia oil post washing - buy online and mix together at home. This keeps the hair soft and lovely.
it took 5 years for DD1's hair to stop growing out, and 'drop' at the back. Finally this has happened. I do brush her hair (using Tangle Teaser brush) every couple of days when I redo her pig tails. Now her hair is longer keeping it tied back or in plaits make a huge difference to knots.
DD2 (2yo) hasn't had her hair cut yet - I'm too scared she will scream the joint down! (She can be VERY loud) :) She has major matting at the back issues.
The Tangle Teezer brush is OK for DD2 - but no longer suitable for DD1 - she needs the stronger Tangle Tamer now (both at Boots).
When the hair is shorter I give it a spray in the morning with a blend of water/NAKED conditioner and if at nursery/school a few drops of tea tree oil. Spray hair liberally and 'fluff' curls with fingers.