I use a Libre now, but have been finger pricking for years until quite recently. Lots of times my fingers refused to part with any blood but my thumbs - only slightly off centre - would always oblige. Result was that, being pricked more often, my thumbs ended up quite sore and bruised. But I am notoriously bad at giving any blood anyway - one doctor even (jokingly I hope) suggested to a nurse that, failing all else, she should just punch me on the nose - that always bleeds very easily! Warm hands help and letting gravity assist by letting hands hang down for a while might allow a little blood to flow.