I use it every time I co-wash or shampoo/deep condition, which is about every 2 to 3 days or at least twice a week (sometimes I go a long spell - a week to a month - without it just to give my hair a rest). I've never used mega tek on dry hair simply because I don't like manipulating my hair at all while it's dry. Using mega tek is not really an exact science so feel free to personalize and change up the steps yourself!
And do buy yourself a garlic conditioner (like Alter Ego) and some garlic pills. Shedding can get ridiculous, especially if you're using mega tek straight up! I'm very slowly making my way back to 100% mega tek, which use to give me like 2/3 to 3/4 inch a month. Currently I'm at 50% and no excessive shedding yet...
Good luck on finding what you need!