Ok my house needs to be painted. BADLY!!! If you remove a picture from off the wall you can see how clean the wall is under that but around that you got this black ring (from the furnace). Do I need to clean the wall first or can I just paint it.How do I clean it I've tried everything. It won't come off.:wall:

I have a metal (w/wood core) exterior door from Home Depot that I wanted to paint. It has white factory finish. I asked guys from HD paint department how do I prep it and they told me to paint latex over factory finish - no priming or sanding needed. I did just as they said, cleaned surface with rubbing alcohol and painted with 2 coats of exterior latex yesterday. Well, it did not adhere well - if you scratch it with a fingernail, it starts to come off. I decided today to redo the job and just peeled the paint off the door in ten minutes - it peeled off as as stretchy film. Now how do I do the job right the second time?