Blu Tack®'s adhesiveness increases over time so take extra care if it's been on there a while. We'd recommend rolling it gently as you can then using what you can get off to dab any remaining bits.
How do you get Blu Tack® out of hair / clothes / my shoe / carpet?
FAQ
Soaking hair in baby oil is one trick to try. For clothes, try freezing the Blu Tack® to scrape as much off as you can, then dab any remaining with a cotton ball dipped in vegetable oil.