Wash inside out and rarely. The chinos, shorts, overshirt and Harrington are all cotton twill, and twill hides dirt well enough that it seldom needs washing after a single wear. Turn them inside out, wash cool with like colours, and you protect both the surface colour and the quiet sheen the weave has when new.
Skip high heat everywhere. A low tumble or a line dry stops twill shrinking and keeps the waistband and hems true. The Harrington's lining and the overshirt's structure both dislike a hot dryer — pull them out damp, smooth the seams, and let them finish on a hanger so they keep their shape.
Press for smart, leave for casual. Chinos take a sharp look from a medium iron down the leg while slightly damp; the shorts and overshirt are meant to read relaxed and need little more than a shake out. Steam is the gentlest way to freshen the Harrington between washes without flattening it.
Brush, air and spot-clean between washes. Most of what lands on cotton twill — dust, a food mark, a splash of mud — lifts with a brush once dry or a damp cloth on the spot, no full wash needed. Treating it this way keeps the colour even and the cloth out of the machine, which is what makes a good pair of chinos last.