I've done a search on the forum and couldn't find much detail about recommendations for what to use here. I found this post from @Nickfromwales back in 2017 but the links aren't working any more so it's hard to know what products they relate to     our liquid screeders have suggest the JG product (https://www.screwfix.com/p/jg-speedfit-jgufhedge-edge-insulation-roll-150mm-x-25m/87019) but this is 4x the price of something like this (https://www.ebay.co.uk/itm/350335173377?hash=it