The 'official' method was to put a nose jack on the aircraft, and lower the nose. The nose wheel could be independently raised by selection a lever in the battery bay. This method was long and arduous - getting a jack out the the 'frame, pumping up the nose wheel using the hand-pump in the cockpit (took yonks), lowering the nose on the jack. After pack fitting, reverse the procedure - took ages ( and made for really sore right arms).
Official 'unofficial' way - sleeves on the main leg's exposed oleo portions, bottle jacks under the main legs. Pump up merrily. This method was also used to facilitate fits of flare crates on the
PR Cans and the nukes on the Strike Sqn Cans.
Hardest part of gun-pack fitting though was getting the special bomb doors (with cut-outs) into position. You could spend several hours fitting a gun-pack, a back breaking job.