As long as we've hijacked the thread to talk about penetrating oil, I worked at a garage that was stocked with products by Wurth and fell in love with Rost Off.
They now have an even more powerful product called Rost Off Max Ice, combines penetrating oil with a freezing/shrinking effect. Worked great on some crusty fork brace bolts on an F650ST recently (after breaking the first one with no p-oil...doh!)
As for the conical washers...any reason you need them off? Some of mine come loose, some don't. I actually kinda prefer the ones that stay stuck--I'll never lose them!