I had a bunch of old garden tools that needed refurbishing, I know that common wisdom says not to paint shovels, but I used a tough paint, and frankly I thought it looked nice.
The real work in refurbishing garden tools was in the handles. I took a lot of time sanding down the wooded handles, but I did take a lot of care in busting the rust off of the metal ends.
I used 120 grit sandpaper to smooth the handles, and used an old cotton cloth (boxers….) to apply a liberal dose of linseed oil.
You need to take care though, because linseed oil gets hot as it oxidizes on cloth and has burned down more than one shop. When I was done with the handles, I actually burned the rag (One corner already was used to buff some knife blades so the brown stain is rubbing compound for those that care…)
It took about a week to dry (well 3 days or so) but the handles are MUCH smoother and easier on my hands.
Do not use varnish, as this tends to cause blisters. I suspect it is because varnish tends to stick to the hands, while a smooth linseed coating slides nicely.