Ensure that your painting surface is clean and dry. For walls and ceilings, interior latex paint acts as a primer. For mailboxes and other metal surfaces, use a spray-on primer in a well-ventilated area.
Prepare your palette by squeezing a small amount of each paint color onto it, about the size of a dime. This leaves you room for mixing colors and prevents wasting paint. If you have a large project, you can always add more as you run out.
Start with the vines. Wet the round brush. Remove excess water. Load the paintbrush with at least two types of green. Do not mix. Test the brush on your palette to ensure the paint flows smoothly without dripping. Add or remove water to the paint as needed. When you are ready, hold the brush loosely and create a wobbly, twisty line for your vine.
Change to the flat brush for the leaves. Prepare as with the round brush until you get an acceptable proportion of water to paint. Remember to use at least two types of green. Lay the brush flat next to the vine and make a short, curved stroke away from it. This creates one side of the leaf. Flip the brush over. Start at the place and curve the brush in the other direction to make the opposite side of the leaf.
Clean out your flat brush and load it with at least two flower colors. Start at the center of the flower. Lay the brush flat and make a short, curved stroke outward. Do this for each petal.
Seal your outdoor art. For small objects, like mailboxes, use several coats of a clear, spray-on sealant. For larger surfaces, two coats of a brush-on sealant work better. If you want maximum color protection, use an ultra-violet protective sealant.