You are right. But, you asked about an alternative to sanding or washing.
Priming is the only thing I can think of, but that's not what you're after.
What we're saying is that a quick pole sand will scuff the surface, break the gloss enough to get better adhesion. If it were trim, or a table or something that needs more protection, then more sanding is needed.
But anyway, I don't know of any tricks other than sanding or washing. There might be a no rinse, spray on product out there.
After work:http://www.winhealth.co.uk/No Rinse Products.htm