Is it just me or did that guy go a bit over kill on the epoxy for that pour, he must have made up enough to shoot the video a dozen times!

Anyway, as far as I know that blue tape is just a decent quality masking tape. Loads of the woodworking videos I've watched use it and they all refer to it as blue tape (in particular David Marks, he gets through a roll a show I reckon). I seem to remember seeing it for sale at ScrewFix a while back.

I used epoxy to fill knot holes in pieces of wood a few times and will usually make a dam with regular masking tape e.g. covering the back of a through knot so all the epoxy doesn't run out. The epoxy doesn't stick very well to the glue side of the masking tape but it's a long way from perfect. I always sand it down flush so I've never bothered to try and make it stick less. Talking about sanding it flush the best tool for this is a belt sander and that would be perfect for taking off the meniscus with the minimum of work too.