Post wash loose hair stretches best when I follow my Mum's old school way of taking it out and restyling it every few hours after washing. After moisturising and sealing I usually chinee bump (bantu knot), then a few hours later add some more lubrication if needed and canerow, then at bedtime do 2/3 big canerows - by morning my hair will be almost fully stretched. Time consuming, but it works for me.
Everyday loose hair stays stretched by either doing 2/3 big canerows or flat twisting before bed. If I do twists on their own without stretching them into a bun, my hair will shrink up in the night.