Great to hear! I had a DC28 brushbar which was rusted badly. I was afraid to use WD-40 on it, so I kept dropping in a bit of electric motor oil into it, spinning it and wiping out the muddy grime. Did that about 100 times.
Haha, remember WD40 is only oil, it's designed to oil and also clean, you can use it for all sorts of things... Starting engines, driving out water, oiling etc... It won't damage anything, very good stuff :)
I've used it to clean whole Vacuum's before :)