Having huge difficulties getting a straight line where the wall meets the ceiling when painting the walls a different colour to the ceiling. Have tried masking tape - it pulls off the paint it's attached to (it's dry and has been for over 24 hrs. Have tried a straight line gadget from homebase (like a plastic ruler) but paint seeped behind it on to the ceiling. Have tried by hand with an artists brush and it still looks rubbish! There must be a great way of doing this! I'm desperate to find a method that works! Help!