Yeah that stuff is brutal. Used to use Gunk on my older cars many years ago. As for the smell that will go away eventually. Try going to Home Depot and buying a gallon of Zep orange cleaner. This is what I do a couple of times a year. Wet down the engine compartment with a light spray of water. Get a spray bottle and spray the orange cleaner all over and use a damp cloth or sponge and lightly wash everything. Give it another light spray of water to rinse it off. Towel dry as best as possible. Then get some "Stoners Trim Shine". You can buy it online. I have used products like Stoners trim shine to spruce up under the hood. Get some, spray it around and wipe off the excess.