I have been put in charge of buying our paint for our pool this year. The last time we painted it we used National Pool Guard with EHB. I am looking at a different paint because we are going to be painting not one but two this summer. I was looking at Zinsser Swimming Pool Paint as I can get it in 5 gallon buckets. BUT....... I need to know if I can paint over the National with this paint and i cannot find anyone that knows. In our area there is only one pool maintenance company and they have not called me back.