If you could reach up the slope with your mini x then an auger on it would work .
They make a one man auger on wheels but it may be too hard to move on that slope.
Or the old fashion way. Shovel.LOL
2 good shovel guys could do 30 holes an hour. I think a team of 8 guys ( 5 digging , 2 planting, one moving plants and cleaning up) should be able to do 500 per day. If they like to work.
I personally would use the auger on the mini ex. You have them for the dingo so it should be easy to retrofit to the 430.