For steady hands I guess it's the same way you steady an M16 - breathing control, tuck in elbows, posture, and use a tripod/monopod/bipod(lol) if necessary. Sandbag even.
If still cannot then I guess no choice. ADOPT PRONE SUPPORTED POSITION! :bsmilie:
But seriously, when you say taking photos for long time, do you mean long photo shoots, or long shutter speeds? You'd definitely need a tripod for long long shutter speeds.