I gather you have air suspension, you could use a floor jack, raise the body from the bump stops and insert wood between the bump stops and the axle a little at a time.
or use a set of "T" couplers on the air lines, you can use them later as self rescue if you plan on keping the air.
any how if you go the second route you need 4 1/4 inch t couplers and 4 schraeder valves to thread onto the t piece.
cut your air lines going to the bags, and istall the t. use the schraeder to inflate and you are done. for a better idea look up M.A.R.S (manual air recovery system)