What’s the best insulation solution for rigid metal ducts that are sweating in an old semi-finished basement?

I am in the process of convincing the homeowner to spend the money in upgrading this 1960’s basement.  Airsealing windows and rim joist, upgrading wall insulation, closing up sump well, etc.  Until then, we’re running a dehumidifier full tilt.  It almost does the trick but not quite.

I’m hoping to avoid thick fiberglass wraps, wondering if thinner foam would be more effective in getting airtight.  A quick online search shows MANY foam products with “reflective” in the description, and I’m suspicious of overblown claims.  What product gives the most bang for the buck?