Unfortunately this walk is currently (July 22) closed due to storm damage from the end of last year, and does not look as though it will be re-opening any time soon. The only point of this post is to save you a wasted journey. I wish I had looked at the Drumlanrig website before I had set off.
Did this walk on 23/02/23, and report that the start of the route is still “difficult”, though not impossible. The fallen trees are all along the first section of the route, and it may be possible to by-pass completely by using the return route for a time. IE. Follow this past Drumlanrig Park, then take first track on the right to enter Carse Wood. This track joins the walk at Palmtree Pool. Though as said, it is possible to just follow the main walk, and you will get through, mostly easy, but sometimes a little more tricky. A very enjoyable walk. I have a detailed route description on Walkhighlands website here https://www.walkhighlands.co.uk/Forum/viewtopic.php?f=9&t=116884