Here's a way of holding them in place
Thanks to spu3 and his Make a Spray Can Nozzle Holster using Sugru 'ible for stimulating this idea.
Decided some 2½inch(65mm) corrugated drainage hose on site could clip on to the can and hold the tube.
I cut off 4 corrugations from the hose and after drilling the holes through the corrugations to hold the tube I realised 2 corrugations were quite enough to hold it, so cut it again to give me 2 holders. A cut was also made across the circumference to allow the hose to spread and be clipped around the can.
I angled the holes thinking it might make it easier to extract and insert the tube, but you may prefer to keep the tube parallel with the can.
This clipped easily to a 2½+inch diameter can.
For a 2+inch diameter can I used a piece of the hose left from making a clip/holder for some PVC pipe, cut off 2 corrugations, drilled them and used a plastic wire-tie to hold it to the can.
spu3 's 'ible led to this. Maybe this will led to another idea.
Unpunched drainage hose was used. Maybe hose with holes prepunched would also be suitable. I recall an old vacuum cleaner hose that may have been suitable for the smaller diameter can. I'd be happy to accept suggestions for other/more common? materials, or see your instructables using them