With a Top Bar Hive there's a choice: you could either pull bars one at a time and dribble Oxalic Acid over the combs - spraying the solution might be easier with Top Bars - or dosing the hive with Vapourised Oxalic Acid. I use the latter method - usually once a year when broodless during the winter. This year I'm multi-dosing - but only because I've got a new toy to play with.
Vapourising is far less disruptive than dribbling.
LJ