Share 'How do you mask the soundhole?'

I've struggled with this for a while and can't find any articles or videos showing how best to mask the soundhole for finishing. The Taylor factory tour youtube video shows that they use tape somehow, but it doesn't look well-sealed. Others suggest to blow a balloon in the soundhole, but I find that if you're a applying a wipe-on finish (e.g. TruOil), the proud bump of the balloon gets in the way…