Fuel Bottle Cleansing.

I disposed of white gas that had been in fuel bottles for more than 10 years. I have read that the bottles should be cleansed of the varnish and gum that has surely formed and is sticking to the sides of the bottles. Paint thinner is what is recommended. After a couple of good rinses with the thinner it is further recommended to scrub the insides of the bottles with very hot soapy water using a stiff-bristled bottle brush.

For the thinner I have both methyl hydrate and Varsol on hand. Is one better than the other for the job?

Also, any observations and suggestions would be welcome.
Thanks!