Is the use of thread sealant on petcocks recommended?

Would Never-Dull wadding polish be a good choice to clean fuel tank and fenders?

I'm a new member and just bought my first Hodaka. Any information on brands of oil and at what ratio to mix would be helpful. The bike is a 1974 Combat Wombat and will be used for light trail riding only. I will be using a leaded non-ethanol fuel if that has any influence on what oil is recommended....