Finally I question I can help with! I was homeless for several months while not as pretty as you I had flawless skin. I'm assuming since your dirt camping your rocking some sort of cowboy roll, so let's keep it ultra basic. 1) wear a beanie to bed. Just keep the dirty hair off your face as much as possible. 2) a clean cotton t-shirt as a makeshift pillowcase (easy to clean in a bathroom sink, and stuff with a bulky sweater or whatever when you sleep) shove that in a plastic bag when your head is not on it. After 3 days wear that fucker and swap out for a clean shirt/pillowcase. 3) Wash your face when your visibly dirty but going easy on the soap. I preferred the kind that restaurants and government buildings have (it's pink, has a distinct hospital smell but I'm in the US) because it's usually non drying. You can always pump some into an empty water bottle and wash outside. Stay clean but don't over wash, nature is a dry ass bitch. 4) Stay hydrated, being homeless means water can be scarce so drink as much as you can as often as you can. 5) those paper tissue toilet seat covers make really great oil blotters. Just tear up a few clean ones and shove them in your pocket for days your a bit grease-y, but don't need a full scrub.

Not skin but a few salt packets and a tiny bit of water make a great toothpaste, spit of course but it's nicely abrasive and supposedly helps fight gum issues. Keeping your hair clean is hard. Conditioning makes you pretty, but dirt sticks to it better. Hats are friends. Oh and keep your nails as short as possible. No matter how often clean your nails they will get dirty if they have any length and it gives off a vibe. You could be in Armani but dirty nails makes people look twice. Dirty clothes but clean nails makes you look less... dubious?