I rarely bother to wash my finger before finger prick testing when out in the hills, often for 2 or 3 days and night. Sometimes finger is clean because my hands are wet due to having just had to use hands to extract myself from a stream / burn / bog / marsh on mountain marathon. Then the issue is removing water, so I usually shake hand then blow on finger. Quick and environmentally friendly, as no waste produced. On summer evenings, standing in a stream to wash feet, hands, groin etc is cold, but a rare pleasure in our world of hot showers in bathrooms. Obviously no detergent to pollute watercourse. For washing cooking & eating kit, take water from upstream of body washing location, downstream of drinking water collection point, and dispose of soapy water into toilet or into ground at least 50m from watercourse.
I'll be a volunteer marshal on Dragon's Back Race in Wales [Conwy to Brecon Beacons] June 2015, and based on experiences in Sept 2012, I know that there'll be 1 or 2 nights at Conwy youth hostel, then 1 night in farmer's field with access to stream, 1 night at a campsite with shower block, 3rd night is mystery, as location is different in 2015, 4th night at camping field with lovely shallow river for sitting in, 5th night camping in a farmer's field below a castle and banqueting hall, so access to toilets with hot & cold tap water.
Overnight campsites used by D of E expedition groups nearly always have access to a stream for washing or at least a standing tap, if not a washblock. If relying on chemical toilets, some have water, soap and paper towels [and / or toilet paper] which is OK. Alcohol hand wash is less helpful.
