You can braid them into four or six square plaits, and put ouchless elastics at the ends. Apply shampoo (some pple like it diluted; I use it neat) to your scalp...after wetting your head. Concentrate on massaging your scalp. Fingers should go between the braids and clean your scalp. When you're done cleaning your scalp, spray water through your head and hair hang down so the shampoo runs through the hair. Squeeze your extensions as the diluted shampoo runs through your hair to clean, and continue till all the shampoo is out. Repeat if necessary.
The way I apply conditioner is to put all the braids into one single plait and then pull out a few at a time and apply conditioner on the part where my hair is concentrating on the upper end of my hair not the extension on each section I pull out (Remember it's the ends where the hair is the oldest and needs the most TLC). If you will do a DC with heat, wear a cap letting hair hang down (a low braid if you want - coz this way the conditioner drips towards the ends that need it most). I think putting conditioner on hair and not scalp helps prevent build up at the base of braid. In fact the bottom 1/2 inch of braid will do OK without conditioner...another way not to get build up, IMO.
If you feel safer putting back into 6 single plaits before rinsing, do so and add the elastics...but use the same gentle squeezing motion to rinse out conditioner.
I always finish with ACV... dunking my head into a solution of 1/4 cup and in a basin of water with 20 drops lavendar EO and 20 drops of rosemary EO and liquid sage when I have it. While my head is submerged, I gently massage my scalp. This will remove residue so you don't have itches and it's good for your hair too.