I had this piece of barn wood. My husband cut it into two pieces for me.
I painted them with a heavy dry brush of white pretty much where I was going to apply the transfers.
Then I applied the transfers.
It was a very rough surface and slow going. It wasn’t easy to apply but in the end it all applied and adhered perfectly. I sealed everything with Wise Owl Salve.
In hindsight, it would have helped to seal the painted area first, but I just took my time and at times actually used my finger underneath the plastic sheet to get over a particularly rough spot and it worked out fine.