BG Quick Clean is to remove varnish in HLA and maybe some ring varnish.
Sludge usually cannot be removed without a pick and shovel and removal of the individual components to the parts washer...............still need tools to get to the chunks.The generic kerosene and pine tar oil products usually don't work well but after a dozen treaments can help some.
Careful of the fluro, bromo, chloro [halogenated] hydrocarbon solvents and PCB's, as Pancreatic Cancer of the handler is common after exposure.
http://aje.oxfordjournals.org/...9/841
There is no magic bullet to clean up years of abuse other than daily/weekly oil changes.