How best sort flaky paint on rendering

Hi guys

I just posted this in the builders thread, but then thought it might be better here.

Im just buying a house and its smooth rendered and in quite a few places, then paint is bubbling up where its rendered. So after scraping the old loose paint off is there anything i can use that will make the paint stick better so i dont have to keep doing this all the time?

Or any type of paint that seems to stay on better?

I can look forward to a redoing the whole lot as the colours wont match lol

thanks

Gaz