First, never (!) use paper towels on plastic windows. Paper towels are made from pulverized wood products and as such, easily scratch them to the point that the windows will eventually turn opaque and yellow.
Rinse the dirt off and use a mild soapy solution with a soft cotton towel to clean them. Wipe them dry with a barely damp cotton cloth, dry stiff cloths can scratch. And never wipe dirty windows with anything, the dirt will scratch them. No squeegees either.