I'm a F-A-N of your work. I think you're brilliant. In fact, I know you're brilliant. And you better post this with my question I'm about to ask. I'm going to paint an on-going mural of characters I designed on some plywood/chipboard stuff that surrounds a building in my neighborhood. Since you're a mural expert (and I am definitely not), here are my Qs:
(1) should I prime the surface?
(2) do brushes matter?
(3) does paint matter?
(4) should I put some finish-coating-something at the end to protect it from all the evil weather?
A. Dear Murally Challenged,
First off, thank you for the kind words. You must know me and therefore know that flattery will get you everywhere with me.
The short answer to your question is No. None of it really matters. The natural predator of the mural is not the sun or the rain. It's tagger. You will either spend countless hours working back over paint pen scribbles. Or the mural will eventually fill in with paint roller blocks of color as the tags get buffed out.
The longer, more hopeful answer is Yes.
Though priming the surface takes more time on the front end it saves time when it come to the actual painting. Painting on raw plywood or chipboard can be frustrating. The paint does not want to move across that surface smoothly and the brush snags on the splinters. I have found it to be an unpleasant experience.
Priming also requires less paint since it's not getting caught up by, or absorbed into, the wood. It will also help the paint stick to the surface longer. The primer should be applied in a few thin/ water coats. Each coat thicker than the last. This way the primer can soak into the surface and hold tight. The final layer can be thick as you'd like. Being outdoors and on a large surface these layers should dry quickly. By the time you reach the end you'll likely be able to start at the beginning with the next layer.
Brushes do matter. But you can get away with a lot on a large scale. I'd encourage you to use the right brush for the job. If it's a big area use a paint roller. Need a little more control but still working in a large area, use a large painters brush. I love to pick up the variety packs of house painter brushes at the hardware store. Generally, the bigger and cheaper the better. I tend to be hard on my brushes on a larger scale. It's always good to have a few detail brushes on hand but usually not smaller than an inch wide.
Not that you asked but small containers with lids are great to have on hand for mixing up large amounts of color than can be saved and used again. Also a couple of larger buckets filled with water are great for cleaning out your brushes. I tend to have a first rinse dirty bucket and a cleaner final rise bucket. They are also good for holding brushes and supplies on your way to and from the site.
Paint matters in that you want to keep it consistent. Acrylic and latex mix well with each other. Enamels are great because they dry so fast. However, like oil and water the water based acrylic paint won't chemically bond to the enamel. If you are going to mix the two I'd put the enamel on after you've blocked in with the acrylic. Most spray paint is an enamel. If you use the spray can please wear a respirator for lung safety. You don't want your body to have to filter those fumes or particles.
In general the higher quality of the paint the longer the colors will stay true. But there is only so much one can expect from color when it's exposed to the sun and the elements. But as I mentioned earlier, those aren't the things that will damage your painting.
Acrylic and latex will be the most financially friendly. Spray paint adds up real fast but it is convenient if you have a feel for it. There are other paint options of course but I think these two lend themselves to the process the best.
There are UV protective coatings out there. You can find them at most hardware stores. It can help protect the surface from water and sun. Some tend to yellow when applied in thick amounts.
Feel free to send photos of the finished piece. I'll post them so people can check it out.
Hope that helps,