Clear the flooring around the molding to create comfortable and easy access to it. Put painter's tape all along the wall and around the room at the top of the molding. This will keep the molding paint off the wall.
Mix the paint well. Take the flat shielding tool and lightly force the blade between the bottom of the molding and the flooring. The shielding tool will protect your flooring from paint. For crown molding, put the shielding tool between the ceiling and the molding below it.
Starting with the largest part of the molding, spread the paint evenly along the edge of the shielding tool. Don't worry about the remainder of the molding right now.
Lift the shielding tool and clean off any excess paint with a dry cloth. Make sure no paint is on either side before moving the tool on to the next section of molding. Continue this process around the room.
Return to where you started and paint the remainder of the molding, making sure not to get too much paint on the tape protecting the wall. Be careful as you paint; the tape only offers a small amount of protection.
Allow the paint to dry. Examine your work and look for thin spots or to verify the need for a second coat. Once the molding is painted to your satisfaction, remove the tape from the wall.