Hi Nigel, Hollowing out a branch can be done a variety of ways. The scorp or the draw gouge is not one of them. The foredom I mentioned can give you the delicacy of a dental instrument. It can offer a small hand piece with a small bur if that's all the carving your doing. The foot peddle allows you to keep your hands on whats important the tree and the tool. The dremel will do what you want, but in my opinion not to the same degree of ease and quality.
If all your near plans for carving are just the branch, you could.......
Use a small gouge or hand pick to start a pilot hole in the area you want to carve. Take a small diameter drill bit smaller than the hollow you want to create. Then hollow the branch out, followed up with a pick, craft knife, or any other small suitable cutting tool to detail the hollow.