Couple friends asked about the plastic-to-wood process so I want to share it here. It's a combination of various methods that I found online.
Step 1: Scribe the planking.
Obviously, this step is optional. I like to see the individual planks with shadows in between them.
Step 2: Apply lighter brown shade.
I used a mix of Revell Aqua color 88 Ochre and 371 Light Gray (80% of Ochre to 20% of Light Gray). I applied it straight to the bare plastic without primer. No need to go for even coverage. In fact if you can see the variation in color that's a good thing.
Step 3: Apply darker shade of brown to individual planks
For even better color variation I mask individual planks and give them at least two different shades of brown. As you can see, the color variation in my case is subtle but you can make the contrast bit more visible if you want.
Step 4: Apply Oil paints
This step will turn the plastic to wood. I use Koh-I-Noor's Raw Sienna (I also use Burnt Sienna for the darker shade of brown) straight from the tube. Many recommend to use acrylics for this stage but I love the fact that oils give you plenty of time. Also some recommend to first put the oil on cardboard so that it can soak the oil and then the pigments dry faster, but for me the oil guarantees that I can play with the piece for a longer time and also it flows much nicer into all the corners. Two blobs of color like you see on the picture is enough for this large piece of plastic.
The secret tool to use here is the cheapest and hardest toothbrush that you can buy. The stiffnes and size of the brush is a reason why you can see the wood grain and variation even if the plastic itself doesn't have wooden texture.
After some time (20 minutes or so) the tootbrush will start to peel the color off a bit so even if you start with some darker shade of brown, eventually you'll get lighter tones. You can use this to make various spots a bit brighter to give it even more variation.
Let it dry for couple of days.
Now you have two options:
1) When it's dry, seal it with the semi flat gloss coat and apply filters/washes as you want
2) Apply oil wash into recesses without sealing. Beware that the underlying oil paint will mix with the wash so you need to be carefull but it can give you even better results.