The only ‘paper ‘ unite failure was with a top colony too weak to chew through the slitted paper. They clustered in one corner and were still there when I checked. Tearing the paper solved the problem as, by then, the aroma from the bees below would have permeated the bee cluster above.
I’ve also united by inserting an OMF between the two sets for a day or so, before removing.
Was actually two meshes - so no flying bees from top or bottom of the hives when moving them across. Plenty of options.
A liberal sprinkling with icing sugar is just as good as spraying with air freshener or after-shave or whatever.