I had the same problem. Blocked drain pipe and water getting in the tank sometimes after washing the bike after openning fuel cap. Told my dealer and they replaced the hose. But for some reason and never tested it until 2 days ago when cleaning the bike after some fucking bird decided to take a **** on my bike near fuel cap 😄. I've managed to unblock it somehow with a bit of soft wire by pushing it through the pipe. It helped but eventualy will try your method.
How hard is it to remove the tank ?
It's more of a pain than on most bikes but not the end of the world. Seat off. Take off the tank cover, two screws on the sides, four on the "wings" and two push studs in front of the seat. I removed the coolant bottle cover and the cover on the other side - three screws each - you might not have to. Then the inside of the "wings" and the ignition barrel cover. Finally two bolts on the bottom rear of the tank and you can lift it. I didn't disconnect the hoses just straightened the hose with it lifted.