Need help with what type of paint will hide rendered joins on a feature wall.?

We have just had a large feature wall made out of blue board near out pool done by a professional landscaper. That was all good and well,( no more peering neighbours Ya Hoo) Then it came time to paint it, however where the landscaper has rendered the joins is very visible now that the wall has been painted. So can anyone give me some idea's on how to hide these marks, any special types of paint etc... We don't want to have to have it all rendered... Please help