The issue you have is the sloping trigger block. Unless you have a fitment/gizmo to allow the sloping block to fit snuggly in a compressor then you can get by without a compressor ... although some people have made such a gizmo.
Personally I do not use a compressor for the Airsporter or Mercury but do use a padded vice. Clamp action or trigger block in vice in order to unscrew the block or action; take care to have good control for when the spring releases. If you do not know what spring is there or what preload to expect, assume the worst and wear leather gloves and put a towel over the action as you release it.
Re-assembly is basically the reverse ... check out the Idiots Guide sticky over in Collectables: thread 39 / 40
Cheers, Phil