Gustofer:

I've since sold both, but I used to have a post hole digger and a 3PH backhoe.

The PHD I parked in the barn with the auger vertical and the gearbox tied to a post so it stayed that way. I could back up to it and lift the boom and pin it into place with the gearbox still tied to the post to keep it from flopping around.

After the boom was pinned in place I'd untie it and wrassle the lower arms into place. Still not easy, but the easiest way I found.

On the 'hoe, the secret for me was to attach the fixed upper mounting point first. Get close enough to hook up the PTO driven pump and then use the stabilizers to tweak the mounting hole left/right up/down to get it close and then the boom to roll it into position with the hole lined up. This with the lower arms up far enough to slip the pin into the top mount.

After that, between the stabilizers, the boom and the 3PH lever, it was easy to get the lower arms in position.

I kept it stored with the bottom of the hoe frame sitting on a 6x6 on top of two old car rims. This kept it at close to the right height. With the bucket rolled all the way back/open (to cover the cylinder rod and prevent rust) and the dipper swung out to form a triangle /^\ it was stable and gave me the leverage to tweak the position when mounting.

I got so I could mount/dismount in about 5 minutes unless it shifted position over time (or from the sheep rubbing on it...). Important when I was doing landscaping as I'd often change gear 3-4 times a day.

Dismount was just the opposite: Blocks/rims in position, unhook the lower arms and then use the hyraulics to jockey it around until the top pin was loose.