Do not use any blankets/sheets/towels as with most other animals. Porcupine quills have barbs on the end and if a blanket is put over them the quills will get stuck in the material. Use hard plastic objects like a plastic bin lid, shovel, cardboard, or brooms to scoot the animal into a holding container.
Baby porcupines are born precocial, eyes open and fully furred with soft quills that harden up within a few hours. Mother porcupines will leave their young at the base of the tree they are foraging or resting in; always look up to check for mom. She should collect them within a few hours or before nightfall.
Porcupines naturally move quite slowly and seem to waddle. They cannot throw their quills, but will use their tail as defence to slap quills into predators.