get yerself a midget trowel mate, theyre about 8"x2" anything that wont do you can use a 1" scraper....end of the day its a lot easier to take off the architrave if they want it perfect, you have to explain why to em tho and if they start givin you the old 'well are you a plasterer or not?' shite walk away from it cos some people seem to think they know everything...
little tiny acute corners you can get with a 'leaf and square' do a search for em...handy when you need em...