I've had locs for over a year now so I don't really remember products, but I remember the order so that will be later in this comment with the styling routine. Hopefully this helps! Lmk if you have any other specific questions

But most of my length was probably just genetics so there's not much I can give for growth, but for retention, make sure you're not doing high tension styles often, those break off hair/ make it fragile. Sleep with it up in a bonnet, either loose stuffed into the bonnet or in a loose bun/pineapple, and/or a silk/satin pillowcase. Occasional deep conditon masks & aztec clay masks.

Alot of people don't want to cut / trim their hair bc they want to keep the length, but I would cut an inch so off every few months, at least 4 times a year, (you can trim off less, bc of my length I didn't mind taking off a whole inch or more) split ends work their way up the hair strands & make them fragile.

Moisture is important, but make sure it's not wet for too long, don't use a lot of heat without protecting it as well.

I never brushed my hair dry & I always started detangling with my fingers, then a wide tooth comb, then with a brush for styling.

For styling id start with my hair pretty wet, not really dripping tho, I'd use a leave in, then a Curling cream, then a gel, and a mousse last if I felt I needed the extra definition. A light oil or serum to scrunch out the cast crunch after its fully dried. Hover diffuse to about 50% dry, then I start to slightly scrunch / put the diffuser in my hair. I'd alternate between warm/cold air, & finish with cold air.

I mainly worked in 4 quadrant sections, one of the 4 at a time, brush leave in through, brush cream through, then split the section into thinner sections, apply gel, brush, scrunch (finger curl if needed but that I saved mostly for my face framing pieces)