It's actually a really easy thing to do. The pen came with loads of different tips, which I will have to play around with.
I'm quite pleased with the results and of course (apart from the cost of the pen which was a gift) completely free! I'm now on the look out for another suitable log to make some more.
On a completely different note, Mr D cooked a fantastic roast chicken dinner for our guests on Saturday night, so I boiled up the carcass to make stock and pick over the bones for dinners for jet.