They might be a bit savage spinning at 10,000 rpm in an angle grinder!
I have a brush that I use in my battery drill. Unfortunately I didn't keep the packaging, and it doesn't have the manufacturers name on it, but I used it to do a lot of the alloy on my engine and it will do in between the fins as well.
The bristles are a red fibre type and they are long lasting. The brush will polish the sand cast alloy and leave only minor 'brush marks'.
It's also very good for cleaning nuts and bolts and can be used with metal polish.