If you've got air suspension, you need a shock pump. They give you control of the high-pressure, low-volume air spring inside the suspension components. Make sure you choose one with the correct air pressure range as rear shocks usually require much higher pressure than forks.
This is an adapter for your SKS shock pump
Will fit Rockshox and Sid shocks
Buy SKS Accessoriesfrom Chain Reaction Cycles, the World's Largest Online Bike Store.