Getting the best flow from latex paint on trim and doors: 1. Be sure the trim is clean and free of all oily dirt (handprints, accumulated airborne cooking oil); consider washing all areas to be painted, using a detergent and warm water, then rinsing. Sand all areas that are at all glossy, to promote adhesion of the new paint; however, if the previous paint may contain lead, do not sand it (so as to not put paint particles into the air), and consult with the EPA (1-800-424-LEAD) for guidance. 2. Apply an interior stain blocking latex primer (not a PVA wall primer). Use a quality polyester or Nylon brush; apply it in heavy coats, and do not keep brushing each area... fewer strokes are better 3. Allow the primer to dry preferably over night. 4. Choose a top of the line interior latex satin, semigloss, or gloss paint, depending on the appearance you want. Be sure to have the paint sales person put the paint on the shaker even if you are not having it custom tinted... the shaking will improve the paint's flow properties, if you use it in the next day or so. 5. Use the highest quality 2" polyester or Nylon brush you can find. 6. Pre-dampen the brush with water when you first use it, then remove as much excess water as you can. Dip the brush into the paint, 2/3 up the bristles. Work the paint into the bristles on the inside surface of the container (this the first time using the brush on this job); re-dip the brush in the paint, jiggle the brush so excess paint runs and drips off, but do not wipe the brush on the container rim... keep the paint on the brush. 7. Apply the paint heavily, and with just a few strokes, then get more paint from the container and continue. First stroke is from the just painted area into the dry (unpainted) area, and the second stoke is back into the painted area. Go onto the next area. Putting the paint on heavier will help it flow out; but watch for runs and "sagging"... if you see this, put on a bit less paint. For doors, removing from the hinges and supporting horizontally for priming and painting is often worth the effort, to get a very smooth finish. 8. Adding a small amount of water to the paint (and stirring it well) will improve the flow, but should not be necessary. It may make the paint sag too much.