Although half the states allow handwritten wills to be signed without witnesses, both Oregon and Washington insist on two witnesses. The only exception is if the will was signed, or the testator lived, in a state that does allow handwritten wills.
Also, states that allow handwritten wills may insist on the entire will being handwritten. There was a case in California many years ago in which a millionaire had a rubber stamp with the name of his estate. He used the stamp in his will. The California Supreme Court said that ruined the will. (The legislature subsequently relaxed the requirements, but it was too late for the millionaire.)
In any event, it’s probably a bad idea to use a handwritten will except in an emergency, as it’s very easy to make a mistake. (When the emergency does happen, it’s better than nothing if the state allows it. In one case from Pennsylvania, a man suffered a heart attack, grabbed a piece of chalk, and wrote a will on the surface of his desk.)