River crossings?
There are only a few required crossings on the Paine Circuit. Normally they are straight forward, but there is a slight chance you may be challenged by some.
When there is a chance of falling into water, unbuckle the waist and chest straps on your pack.
Consider bringing a pair of footwear which you can use to wade. Old light running shoes are best but most hikers use TEVA-style sandals. Cross first without your pack to check the route. A walking stick or hiking pole is useful for balance.
Plant each foot carefully. If you are nervous, ask a more confident hiker to carry your pack. A group is safest walking across together, elbows linked. The strongest / heaviest person is upstream.
Blisters?
Wear comfortable, broken-in footwear. If you feel a hot spot, stop & take off your boots. Put your feet into cold water when you get the chance to cool them.
Wicking inner socks may help prevent blisters.
Bring Leukoplast or Elastoplast bandages, duct tape & any other blister first aid products you like, just in case.
If you do get a blister, using a sterile needle, prick the blister a few times. Drain without touching the fluid or holes. Seal with liquid Betadine and, when dry, place some tape over it. We usually use duct tape it's inexpensive and seems to stay as well as anything else.

Duct tape.
Insect Bites & Stings?
Mosquitoes can be a problem in the early summer. We did not see many in December (usually the wind blows them off) but tiny flies were a nuisance.
Bring long pants and a long-sleeved shirt. Tuck pants into your socks and shirt into pants. One of our hikers swears by his unlined nylon pants & cycling jacket.
Insect repellent containing DEET may help.