Every year I have paid a sprinkler system company to "winterize" my sprinkler system, which, as far as I can tell, simply means they blow out the lines with an air compressor. I want to save some money and do it myself. (I could also use an air compressor to blow out lines to swimming pool and blow up inflatable pool toys, so I would make use of it.) Anyone have advise as to what type of air compressor to buy.. i.e. they seem to be rated in terms of psi/cfm/hp/gallon, etc.