Hi John,
I believe that most race waxes are designed to give you a boost for the single race run. The philosopy is -- it should last for this run and if you need a fast skis again then wax some more. If you are a recreational skier, the race wax does not matter.
I tried some of the sprays -- they last for a couple hundreed feet and it's over. The same is true for the solvent-based stuff like NotWax and other gizmos. The wax must be absobed in the pores of the sintered base (make shure you are not having the cheap extruded bases since waxing them is pretty much useless). Also, I think that most sprays in the racing variety must be applied as a final step to already hot waxed and prepared surface.
I suggest trying all-temperature hot wax like
Hertel since you don't have to worry about the air/snow temperature.
Nothing substitutes hot waxing. Don't be afraid to srape the bases, the plastic srcaper is harmless. The bases are sraped much more by the snow while skiing.