You should first wet down the entire front of the vehicle to protect the paint and keep it wet. Then you should use baggies to cover the vital electrical parts, overwetting WILL cause problems in most cars. A little extra time can save you a lot of money. Use a biodegradable cleaner like Castrol's degreaser/cleaner or full strenght Simple Green. DO NOT USE SOLVENTS. They are flammable, and don't use WD 40. Yes, it disipates the water, but it will also attack all your rubber belts and hoses. It is better if the engine is warm, not hot, and let the cleaner dwell for a few minutes. You can use a narrow brush to aggitate the dirtier areas. Rinse off the cleaner from the engine and anything that splashed on the paint. Blow off any excess water and let it dry. Once dry use a "water based" dressing and let the engine run until it is baked on.