The potato was greasy because you added oil to the pan. That cooled down the contents and allowed the potato to soak up some oil.
If you put more oil in the pan to start and get it hot before adding the potato, you shouldn't have that problem again.
Also, after shredding the potato, wring out as much water as possible by rolling the potato up in a towel and twisting the towel to wring out water. This will speed up the cooking process.
Instead of green onion, use yellow onion, garlic and some paprika with a dash of cayenne.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan