As mentioned earlier, Coelan is very thick, and the instructions given by the manufacturer do not work well in practice. It takes a lot of diluting, a lot! For brush, I used 0,5 liter thinner for 1 liter Coelan. For the spray gun, I ended up with 1 liter thinner for 1 liter Coelan, which was a lot more thinner than I had ordered, so I had to order more in a hurry. I didn't use a roller, but I would think the same amount of thinner as for the spray gun will be right, maybe a bit less.
Because it is the layer thickness that is decisive for the durable result, it takes a lot of Coelan - I ended up using 30 liters. However, a lot is wasted when using a spray gun, which is probably the reason why I needed more than I had expected. I gave the vertical surfaces 14 coats, the horizontal 12 coats with the spray gun.
A problem with using a spray gun is the spray mist, which causes the horizontal surfaces to become dull, if you spray for a long time and don't have enough ventilation (I used proper protection). So I had to split it up and spray first the vertical surfaces, and then after it had dried properly, I masked it and sprayed the horizontal surfaces. The drying time is quite short, and if you do not have to walk on the surfaces, you can put on several layers in one day, but remember to remove insects and dirt before putting on the next layer. This is most easily done by sanding lightly with sandpaper grain 220. After a few coats, the stain will be gone.
Before the last 4 coats, the surface must be sanded thoroughly in order to get a smooth finish. Coelan tends to become a bit uneven, and it gets worse as you apply more layers. Use grain 100 to 120 to sand the surface, and if you are still within the 14 days where sanding can be omitted, finish with grain 220. You if you spray or use a roller, you need at least 4 coats afterward, otherwise there will be visible scratches, especially if you don't finish with grain 220. If you use a brush, 2 coats should be enough. And you have to wipe the surface very thoroughly after to remove abrasive dust - it is extremely difficult to avoid dirt on the surface, even if you are very careful.