The de-icers were an anti-icing system. We would switch the pump, at the FE's station, to cyclic operation if we thought we were going to encounter icing conditions, wetting the flying surfaces with AL5, making it difficult for ice to accumulate. If the icing started setting off the alerters or we could just see it adhering we could set the pump to continuous. In that selection it wasn't going to last very long though, so we always tried to get out of the weather as quickly as possible. We also had to fly at specific speeds when using de-icing fluid, this was to ensure that the fluid would flow back over both the upper and lower flying surfaces. It was always beneficial to do a set of pre-flight checks on a dry day, as you could then see from the puddles appearing under the porous strips if any of them were blocked/failed.
I was a Shackleton AEW nav/captain for 9 years, until 8 Sqn folded at Lossiemouth in '91. My day to day bomb bay load was a set of Lindholme gear on the rear carrier, next station had 4 x 5" flares (nasty things!), then we had 3 carriers abreast. The middle one had 4 x Markers Marine and the outboard carriers were fitted Light Series Carriers and each had 4 x Smoke and Flame Floats. The Markers Marine and 5" flares all had RBF collars and tags on them. If we were going to deploy we used to drop the forward carriers and replace them with panniers. The pannier was a large, grey, canvas affair with a grey tubular external frame. I cannot put my hands on any photos at the moment, but I'll look.