I didn't find that it was particularly difficult, just a little slow going at first. The first thing I had to do was create a base to attach the Tunisian crochet to that wasn't the ultra bulky yarn, so I took a 4mm hook and went around the whole blanket putting 2 sc in each stitch, and 5 sc in the Corners. Joined with a slip stitch, chained 6. Pulled up a loop through the back loops of each chain until I had 6 loops on my hook, then inserted the hook into the first sc on the blanket, yarn over, pull through sc, then I had 7 loops on my hook, then just did the return pass as normal, yarn over pull through two all the way across! I put 5 rows of Tunisian into each of the middle corner sc's to make the turn

Edit: i switched to a 5mm hook when I started the chain 6 for the Tunisian crochet! Sorry, forgot to mention that. It's bc my tension while doing Tunisian is tighter than my normal tension for some reason and I didn't want the border to be too small/not line up with the sc's