Say, if you wanted to wash your hair every 3 days, are there any tricks (products that you can use), so that your hair wouldn't get greasy/oily before the 3 days is up?

When my friend (co-worker) gets her hair straightened, it takes a good hour and a half. Once done, she could for 3 days without washing and her hair would still look good (nice and straight), but, depending on how much product is in her hair, it may or may not get greasy/smelly. Is there anything that she could do (use), so, that she wouldn’t get the greasy/smelly aside from washing it during that time?

A certain shampoo (deep scalp cleansing)? Less product?

Anything? Bueller?