Looking for some boots advice, ToT included for pup tax purposes

Looking into getting some boots for Kupo since she likes to zoom like a fool. Any advice on how to accurately measure her paws, and also I see that some of them can cause their dew claws to rub into them, could placing a small cotton swab (like ones you apply face stuff with) between the claw and where it would rub against before putting the boots on help with this issue? Thank you in advance for any advice