Years of rust proving removal?

Hello everyone.I pulled the motor out of my Scamp and decided to clean the engine bay up some.There is stuff like yellow glue and rust check all dryed up all over.I tried varsol and it wouldn't touch it.The paint is good under all this crap and don't want to ruin it.I tried lacquer thinner and seems to work but I was told it will soften the paint.Any suggestions on how to get this stuff off.Thanks