If you use "Rain or Shine" glue you don't need primer, but the glue is colored blue so It kind of kills the purpose of a prefect white gun....
Really you can use purple primer and just put it on the fitting and on the tip of the pipe and then put on glue and put the pipe into the fitting while the fitting is on the ground so your primer doesn't run...
Do I Really Need Primer
Just wrap the pipe near the fittings in some kind of tape, just like painting your walls. If the fitting comes off just add primer and glue it back on. PVC Cement turns hard if it not with Primer, a little came out on mine and it peeled right off.
"There isn't a problem in the world that can't be solved by the proper application of explosives"