Start by removing the pads from the chair. You can unscrew them to take it off. Then spray paint the chairs. While the paint is drying, you can upholster your cushions.
Lay the cushion on a fabric that is big enough to pull around it and staple it down right over the top of the existing fabric. Make sure to keep it pulled tight, and if you're using a fabric with a pattern, keep flipping the cushion over as you go to make sure you're keeping the pattern straight. Trim the excess fabric and reattach the cushions.
Just drill a new screw up through where the the old plastic screw used to be and the final product should look like the image above.