The dry shampoo dilemma.
Here's a trick from stylist Peter Gray: Massage a few drops of a liquid clarifying shampoo into dry strands before you shower and lather up (like this one from Neutrogena). Also, limit dry shampoo to one to two applications between washings, says N.Y.C. stylist Kattia Solano. Any more and "you'll get a buildup of oil and powder."
Neutrogena Anti-Residue shampoo, $6; drugstore.com