I have brought reflexology and massage up in conversation on several occasions, with a view to it opening a short discussion, during which I will often ask or be told about the person's level of ticklishness.
(Pedicures and foot pedicures are good topics for this as well).
My mum is a regular reflexology 'customer' and I have also been for the treatment when younger, so I've gained a bit of knowledge of the subject, not just the foot side, but also head and hands and the crystals used.
A drinking friend of mine a long while ago asked for a massage after a night out - I gave her a nice foot massage and inevitably asked if she was ticklish and playfully tickled her for a short while.
The best example though was when one of my very good friends, whom I already knew was ticklish all over, started talking about reflexology during a pub conversation - I jumped at the chance to offer my knowledge of the subject and to give a demonstration....she was hesitant and mentioned her ticklishness, but I explained that it was more likely to hurt than tickle, so I proceeded to massage her foot knowing that eventually she'd get tickly - I lightened my touch slightly and touched the bottom of the toes, which got the first giggles so I just started to tickle her foot all-out resulting in one of the most brilliant ticklish reactions I've ever instigated and one of the biggest cushion-attacks of the head that I've ever been on the receiving end of!!
TTG