I'm not sure what variation there is on acrylics but I made some straight night wagglers a few months ago which used the rubber/silicone tube as the starlight boss.
I initially intended to leave that part unpainted but brushed onto it accidentally and so I continued to paint the whole thing.
After drying I found I could bend it right over without the paint fracturing or peeling.
I'm very surprised in all fairness, hence trying not to paint it in the first place...
Whatever paint is used I would be inclined to give the tip the very lightest of a tickle with a really fine sandpaper and white undercoat first, especially if going with a flouro colour.