right well i have had lots of experience doing this and can understand what a total frustrating pain it can be.
i have put a clear length of plastic tube the length of the barrel height and a female brass hoselock on the end to keep it in there and stay at the bottom. plastic plumbing tube will be ok, cut the hose slightly diagonal at the bottom so it doesnt get stuck sucking on the bottom if you dont use a brass fitting.
I used the normal 100m 8mm hosereel and bolted it to the floor with two hose guides, but you probably wont want to do that in a newer car. 8 barrels, changing them over is a sure pain, what i usually do is turn of the varistream when it runs out, put the sucker in the next barrel, then disconnect the reel and pump on boost, & wait for it to suck through, then back on the reel and down to 4-5 ish,, and so on.
It would be handly making a doubling up fixing for two barrels at a time. Brass metal ball bearing female hoselock fitting on the reel where it revolves is a must, otherwise the plastic ones break all the time when reeling in.