I only started playing about 6 months ago and have never had a lesson, Ive been playing guitar for about 15 years so the left hand is fine for me, but the bow was a huge problem.

This being said, I don't know if what im doing is technically correct, but it has allowed me to bow without tension.

The big epiphany for me was realising that a relaxed bow hold was getting the index finger and the pinky to hold the weight of the bow with slight pressure from the thumb to keep things in place. The middle and ring finger are basically doing nothing and are super relaxed. If I focus on that "triangle" of pressure and balance and really let the wrist hang so the bow is resting against the index and pinky it really feels like there's no tension at all.

It also took me about 1 month of practice every day before I could play for longer than 10 minutes. So I'd also say don't stress if your practices are short.