Hi" Jan, Well, stand by for all the mail you're going to get about painting bricks ( to some of us, it's the 8th sin ). Ok, well you want to plaster your fire place, first wire brush all the bricks, clean away any soot, that may have built up over the years,. Clean out all the joints about 1/2", mix 4 of sharp sand 2 cement, add water but not too much,( it must be like thick, so it wont just slide off the trowl.) If you want an off white or a pinkish colour, then you will have to mix in some white cement and a red sand, now start at the bottom and work your way up,make sure its even all over ( not smooth ), let it dry for about a week, then do it again using the colour of cement/sand that you like best. ( I know people who have put it on with their hands, the get a real good finish to it, ( if you do it with your hands use gloves).cement is not so good for your hands. there are many ways to finish the outside as I have said , its you that will have to look at it, :o) and good luck... A man from another time.