To gain pulling power you need a double and single block. Anchor to tree go to (Double) block back to a single block also anchored to the tree then back to the double block then to the pulling forse. It works just like a crane were you have a single line pull to the top of the crane then a bunch of loops down to the hook.
No you don't. Winch-snatch block (attached to load)-anchor. Doubles the pull with one pulley.
winch-snatch block - tail of snatch block (attached to load) - anchor. 4x the pull.
Drawback of course is that on the 2x pull you need to pull 20 ft of cable to move load 10 ft. On 4x you need to pull 40 ft cable to move load 10 ft.
(edit) oops - thought that looked wrong.
You need cable from anchor to snatch block (on load) with the cable end attached to another snatchblock. That one has the cable from winch through it to anchor. Maybe someone who can do drawings could illustrate that.
Wench - snatch block (tail attached to cable) - anchor. \
I use my F150 as the pulling power and rigging for 4x pull is a PIA as I have to keep shifting the cable every 12 ft. All my cables are about 50 ft long.
Harry K