The younger the roo is, the easier it is to twist off the spurs. I have done it to a roo as young as a year old and recently to my two two-year olds. Their spurs were longer and harder to twist off and the larger roo bled quite a bit. Don't worry about it being painful. None of the roos even flinched as they were lying on my lap as I was doing it. The older the roo, the longer the nub is. If you de-spur at a young age, the re-grown spur won't be as long, therefor a less dangerous weapon.
You may need to twist very gently, for what seems quite a while, before you see the spur loosen. Be sure to grasp the spur firmly at the base close to the shank. When it visibly loosens, then gently pull the spur off the nub. I rub Bag Balm on the wet nub. It usually hardens in a day or two.
My roo that bled had to be wrapped in vet wrap to protect his nubs from being damaged as they were hardening. He's a twelve pound Brahma, but something of a delicate, but very clumsy flower.