I've done a lot of engine details and find that using an oily dressing is a very bad choice. It quickly attracts and holds dirt and grime. There is a much better solution. My favorite product is CD/2 Engine Detailer. This is an acrylic based substance that dries hard so it doesn't attract and hold grime.

I use a citrus cleaner like Orange Blast first. Spray it in the engine bay taking care to not get it on any waxed surface of the paint as it will remove the wax. Be sure to cover any electrical components and your air intake if it looks like it will get water in it when you rinse. Let the cleaner sit for about 5 minutes to do its thing then spray off with a hose using a fan type spray with some pressure. BTW, If you are doing this in your driveway it's best to park over a tarp as the grease and dirt released will stain your driveway. Maybe do this in the street if possible. If there are stubborn grimy areas agitate with a brush.

Your engine should be slightly warm when you do this to facilitate faster drying. After rinsing you need to dry things. I use an air compressor to blow out any standing water and some old shop rags to wipe off any standing water. Once dry, spray the CD/2 Engine Detailer and start the engine to heat things up and speed the curing of the acrylic polymer.

Here is an 18 year old engine bay I recently did.

 

Damn that looks good