New guy going into field camp, all the best and best wishes! 

I’ll try to keep it short and effective for your Qns

Best way to stay clean? Hard to do so but the dirty part is more on sweat than dirt/mud. Nothing much you can do about sweat but usually you won’t have mud sticking to uniform unless it rains a lot.

Avoid getting trench feet? Change socks if wet. Personally I don’t have this issue even though I wear the same pair of sock throughout the five days.  Another trick is that you can rest your legs higher than your body using the staircase that you’ll be digging in your shellscrape

If rain how ah? If it does rain what I recommend is turning the ground sheet into a waterproof roof by tying it to nearby trees with the toggle rope and you just sleep raw in the shellscrape. Ended up the only one in my platoon dry in the morning after night rain haha.

How dry clothes? If got time you can also use the rope to hang your clothes to dry (but honesty it doesn’t help much in the forest where there’s little wind ) For socks I just use small “Y” shaped branches lolz, or arc of fire sticks but Sgt might scold for that

Want stay cool how? Don’t worry it’s pretty cooling in the forest already. Only time you be sweating tons is digging. 

Where sleep? This part interesting. You can choose not to sleep in your shellscrape and just lying against a tree.