We have experimented with different types of oil for ease of application and durability but by far the superior oil in our opinion is Osmo (shop below)
50mm x 25mm treated batten.
We buy ours ready mixed for less hassle/correct ratios. We use Pavetuf Priming Slurry or Easy Prime (shop below)
90mm x 45mm
We buy ours from gardenlightshop.com, and specifically we use the Techmar Systems.
We have an in-house architectural designer who uses Revit.
We use Carpenter's Mate screws by OSC. Link to their website on our homepage!