Roll the gear to the side, point valves back towards you, push bottom of tanks through restriction first. Always have alternate reg (long hose) close by to switch to 'Just-in-case' (HINT HINT). suggest coiled up in hand as you push tanks by the valves.
real situation where this is required, is considerably differnt to doing it with a huge amount of space around you.
Ian is exactly right...do not do it that way in your pen course...the moment they see you have lost control of your other reg...bang reg change!...if you haven't got it.....good night charlie