Take heart, the saguaro is probably older than you, and hates it when older gentlemen lean up against it.
I've never had to take a long shot at game, though I practice for them.
For years I would practice in the Tillamook forest, shooting across a canyon where I hung gongs at 300, 400 & 500, and another where I could shoot 800. I would use boulders or pin my rifle up against a tree.
I had bipods on my favorite rifles, and never once used them, and took them off.
A friend gave me a monopod shooting stick but that was only a little more stable than offhand.
I use shooting sticks now where I'm crouched on a knee and the stick are canted toward me. I don't know the brand, they were a gift from my brother. They took me some getting used to as far as ergonomics.