The hinges on the boot need lubrication so before starting wanted to ask what the best product is to use? White grease, oil, silicon spray? So many choices so grateful for guidance on what and what not to use.
Two aspects to consider. Firstly, a lubricant capable of penetrating to where it needs to be - which kind of defines the format. Secondly, one that is clean enough not to contaminate anything in the vicinity - esp luggage.
An oil will be easiest. Chances are whatever you find won't be that great. No matter, just re-apply as often as necessary.