Packing for three weeks when you wash on the way
Short answer: Pack for one week and wash twice along the way. That is the only way to keep luggage down on a long trip.
The basic principle
Never pack for the whole length of the trip. Pack for the interval you can wash in, and repeat. For three weeks that means one week of clothes plus a wash every seven days.
What to bring
Seven sets of underwear and socks, four tops, two bottoms, one set of nightwear and a small travel detergent. Choose thin qualities that dry overnight. See bamboo underwear for men.
Hand washing in a hotel room
Wash in the basin with a little detergent, press the water out in a towel and hang the garment up. Bamboo fabric is dry by morning. See bamboo t-shirts for men and bamboo socks for men.
Frequently asked questions
How much detergent should you bring
A small travel size or a few sheets of travel detergent covers three weeks.
Can everything be hand washed
Bamboo viscose yes, provided you do not wring it. Press the water out instead.
What if there is no time to dry
Wash in the evening and hang the garment on a hanger in the bathroom overnight.