Another penetrant you can make at home is a 50/50 mix of acetone and automatic transmission fluid. Some people claim it's better than any of the commercial penetrants. I've seen both components of that mix on the shelf at Walmart, but I've never gotten around to mixing any up and trying it. The only 100% effective way to deal with sticky valve guides is to pull the cylinder head and do a valve job- - - -which the engine probably needs anyway.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!