NEVER, under any circumstances, "put ur lips on the end of the barrel and blow"![:(!]
Even before you put your fuel in, the solvent-fumes from a freshly builkt launcher can/will ignite. IF you think about it, this would be equivalent to putting your mouth on the end of the barrel of a loaded semi-automatic firearm with the bolt locked open.
One of the first things (if not THE first thing) that we stress here is safety. And your suggestion (in my opinion) is completely irresponsible.