The paint is perfect for the engine bay. It has a fairly high temperature tolerance, and the engine compartment doesn't get extremely hot due to airflow.
We don't recommend our touch up paint for brake calipers. Brake calipers routinely reach temperatures higher than 600 degrees, and that requires a special high temperature paint and high temp clear coat. VHT is a brand that specializes in such high temp paint. https://www.vhtpaint.com.