Best way I have found to do homemade fries, shoestring or other is to slice and then soak in ice cold water for at least a few hours. Then dry thoroughly before cooking. I do them in deep fryer and usually with a two stage process.
Using Peanut (if I have it) or Canola Oil I do the first fry is at about 325 until they soften and get like a blond color. Then scoop onto paper towels to dry. Then a few minutes (at least 10 so they cool fully) later they go into 375 degree oil. A few minutes is all they need and then back onto paper towels or a brown bag with some sea salt and sometimes a bit of fresh Thyme.