Double cross

Hey, I've got a question about the Double Cross. The sticky putty it comes with to make the cross stick to your finger—do you have to use all of it, or just a little bit? I used the whole thing, and my pen looked like a mushroom; it seemed like way too much.

Can anyone help me out? Maybe just a little bit is enough. I'm not sure...

Thanks in advance, and a shout-out to everyone!