When people think of using a brush in their engine bay, the initial thought it typically for cleaning. It's a reasonable assumption that you will need to break out a brush or two along with some elbow grease to clean up the average engine bay. You are likely to find baked on grime, fluid and dirt build-up and dust in crevices that a towel or hand just can't reach. Most of these tasks are going to be undertaken with a medium or stiff brush to break-up the grime and shift sand and dirt. But once all the dirty work is done, there is one more task for the brush...dressing. This trick isn't complicated or a trade secret, it just isn't widely publicized.
Take note of your specific engine bay to determine what size brush is going to be appropriate, but the best option I have found is a relatively large brush (bristle area about the size of a fist) with long, flag-tipped bristles. Below is an example offered by Mother's and available at most auto parts stores. These are often sold as wheel brushes, but this may be too large for some engines. Once you have finish cleaning the engine bay and wiped down the majority of the moisture, liberally spray all the non-metal surfaces with your preferred water-based protectant. For me, that's 303 Aerospace Protectant. It leaves a factory sheen that is dry to the touch. It won't attract more dirt and makes everything a little easier to clean. Once you've allowed the protectant to dwell for a few moments, spray the brush a few times with your protectant and then work it into all the surfaces you've sprayed. Where this technique really excels is intricate areas like intake manifolds and on rubber hoses. You get complete and even coverage without protectant heavily pooled in corners. Next, follow up with a microfiber towel to remove any excess and even our the finish. Finally, spray your microfiber with one or two more hits of protectant and wipe the rubber seals along the outer edges of the engine bay. This application method can cut your time to just a few minutes, ease your labor and give you top quality results.
