Engine cleaning Went out for a ride a few weeks ago and it was intermittently raining.I live on a gravel road and she got some mud on her sump case

Oil rad and exhaust.Forgot to clean her and got busy for a few weeksnow the stuff's baked on.I usually use a dilluted mixture of Simple Green and water.Wouldn't take some of the heavier crud off like it normally would. What else would loosen some of the baked on stuff that won't damage the paint or stain the Ti's?Anybody use anything more abrasive than a sponge to wipe off stuff and get in the nooks and crannies that won't scratch? Thanks,I've been using the s100 cleaner. Never tried the brightener. I get mine from a sorta local (25 miles) shop,,,