I used to be a PDI and Make-Ready worker at Don McGill Toyota and while i worked there, i learned the best way to detail your engine bay. Its simple, use ArmorAll, the same armorall you use on the interior, use it under the hood, let it sit for 10 seconds and wipe it down with a lint free cloth, armorall also works as a tire shine
Hope this helps
Detail companies like armorall because its cheap and it does the best clean.
But also it makes it so the engine bays get dirty again faster. So people come back more often.
2006 G6 GT
Mods so far: Black arrow overlays, Chrome recessed grilles, Blue LED license plate light, Blue LED reverse lights, Smoked tails, 20% Tint all around, Red led's for the interior, White led dome and map lights.
Sound System: 4 Infinity Kappa component speakers, 2 Amps (950w total) and 2 10" Kenwood KFC subwoofers, 7" touch screen Pioneer DVD
Performance: Mobile 1 oil, Mobile 1 oil filter