The anger is really scary. I have a part that is physically violent and holds so much of the anger. She nearly broke the foot when she kicked T's office chair. T allows her to vent but the "new"rule is that she can't harm herself or others. She can say anything she wants----she can pace, she can pound pillows she can bite the pillows. She's been quiet for awhile.
Littles turn anger on themselves an hurt themselves in various ways. They don't know how to show anger any other way. I wish they did. They can't even cry. So everything stays inside.
I've worked on re-directing the self harm by some of the same things that have been suggested. Its a long process. Be kind to yourself and your littles as you journey through this,