I use the side mirror of the old Dodge. 
The most stable shooting platform there is!! Just be careful when shooting off the hood not to leave powder burns in the paint.
I was actually given that piece of advice years ago from an old guy from the Midwest that I ran into on my first antelope hunt. He was dead serious when he told me to make sure and put a shirt down before I shot so I didn't ruin the paint on my truck

I use a harris bipod. It's quick and will swivel a fair amount if you have a target that is moving. It's worth much more than it weighs when it's time to shoot in my opinion.
I tried the primos trigger activated walking stick bipod deal one year. Personally, I thought it would be fine for a fairly close shot by not much better than offhand. To many moving parts for me to try and shoot much over 150.
I prefer shooting prone with the harris bipod.