I have pre-sealed the surface with a couple of quick coats of Liberon finishing oil. This helps in case some resin goes on the wood; it is easier to remove. You can stain plywood with whatever you prefer but for this one I have left it raw.
Once set, I use a Dremel with a variety of attachments to just carve away and make it appear like bark. It doesn’t matter if some is flat around the edges as this is precisely how it would appear if sawn from a larger piece. So far the time spent is absolutely minimal. To get to this stage is simply a matter of minutes.
The different colours are by mixing in some weathering powder (dye) with filler; this then gives differing depths of colour when painting. You can also mix in partially so it can look just like bark even before painting.
Next I use a selection of Humbrol enamels (mostly matt) with some dry-brushing techniques on different colours. Just look at bark and see how many colours you see. There are no rules, just do what looks right.
As it dries, if you just wipe across the peaks you get a nice natural finish. When dry, a final 2500 sand across the surface and coat with as many layers of Liberon finishing oil you like. In this weather it dries very quickly and I generally apply five to eight coats. The last one is applied after flatting back with well worn in 2500 grit. I use a spray bottle to mist the surface and a block gently back and forwards; at this stage it is only really dust that is being flattened.
Finding somewhere that is dust free for the final layer is the challenging part. After 24 hours of the final coat being applied I then use my old vehicle detailing machine with a 3M foam pad and a 3M polishing liquid which would be on a par with approximately 20,000 grit. That is not precise but trial and error have shown this one works well. It takes only about 15-30 seconds on a medium speed for the polish to disappear and the shine to show through.