How do you get that white tac/blu tac stuff off your walls?

[ChinUpChestOut]

DS has a load of stuff blutac-ed onto the walls, and we need to re-paint. How do you get it off, when it's old and really stuck on? And how do you avoid taking the existing paint off with it?

And if by accident you have happened to have taken the existing paint off, right down to the plaster, what happens when you re-paint? Do you need to do a little pre-painting on that area first?

I work in training and have to do this all the time.

Use a wee ball of blu/white tac to take it stuff off the wall. Just dab it against it and it'll lift right off.

The worst I've ever been left with is a wee grease mark. Never torn any paper thus far.