NOrmally just warm the engine a bit to help with drying. Then armed with AG clean machine, a toothbrush and a hose I do a bit ata time. Spray on the AG, agitate with toothbrush then rinse with the hose before it dries. That way I don't drench the engine. Not had a problem yet! I find it's often the yellow caps and the washer bottle that come up best, if you can do a good job on those then it's a good start appearancewise. Then vinyl and rubber care, or tyre spray on the rubber hoses. Either spray and wipe, or just spray and leave. Should give an improvement