So I do not wash mini twists anymore because my hair would tangle and break off. However, I make sure that products do not get on my scalp to avoid build-up. One thing I do to prevent breakage as much as possible is stretching the twists. My hair is long enough to gather my mini twists in two ponytails.
I usually get a crinkled-like texture on my mini twists when I take the braids down.
The main thing is I do net wet them. I only moisturize the ends regularly, like every other day. However, once a week, I do not use a shower cap, when I am taking a shower. I let the steam from the shower gently moisturize the entire twists (without letting water directly touch my hair). My hair is in two pony tails when it is getting steamed. This minimizes frizz from the steam. I follow that with a gentle squeeze of a creamy moisturizer into my twists to seal the moisture. I squeeze as opposed to rubbing to avoid handling my hair roughly and that, to some extent, prevents frizzing.