I'll try and describe my spring compressor. It's all wood and doesn't risk marking the gun (Gamo CFX).

Lay the action on bench (length of action down length of bench and screw two blocks of scrap wood, one each side of barrel, so that breech end of cylinder can butt against them.

Two more blocks, one either side of trigger end of action to prevent movement side to side.

Take a piece of approx 1 1/2" x 3/4" x about 2feet long. Screw one end to bench, with screw (forming a pivot) approx 8" towards rear of bench and approx 2" behind rear plug of action. Add suitable packing between this lever and end plug and lean on lever to compress spring, then you can use both hands to remove plug retaining bolt or pin.

Sorry if it's a poor description, I was trained in heavy electrics, not English!
The CFX required about 10lbs to compress the spring and unloaded, it projected about 1 1/2" out of cylinder. I imagine other springers will be similar.

I should have taken a photo, but hindsight is always 20/20!