The Castrol stuff is pretty good, Greased Lightning is pretty good, but the best thing I've foudn was at Lowe's or Home Depot. Sometimes they put it on the isle with house siding cleaners, sometimes it with the Fantastic/409 stuff. Its in a nearly unmarked plain gallon jug and is called M-1 household cleaner...should be about 20-25 bucks.
However, if you dont wanna screw around, go buy a gallon can of parts cleaner and spray it on there...it'll remove paint and all.
For that matter, plain old kerosene works pretty dang good...
The Pressure washer makes HUGE difference no matter what you use.
http://albums.photopoint.com/j/View?u=1617246&a=12411361&p=45146549.jpg
1970 Fastback, 4V 351C, various colors with black interior