Want to paint my concrete garage floor top prevent it continually "dusting" but as its only been down for a month not sure how long I should wait?some paint manafacturers say a month and some say several months,also how necessary is it to apply a sealer prior to painting,I've painted a couple of floors before without sealer with no problems,just wondered if its a bit of old tosh to get some more money out of Joe Public,sealer is nearly the same price as the actual paint! thanks chaps