Tire mounting question

I run 29x15.50x 15's on my duster without tubes. Street/strip car. After I spun a tube air stem off I spoke with a tire guy and he told me he had super pro cars running without them.

What he did tell me to do is to: Take pure dawn dish soap too the inner side walls of the tire before you mount them on the rim. What it does is seals them from leaking down. Then car can sit all winter without hardley any air pressure leakage.