A free radical cure catalyst composition is provided that includes a free radical cure catalyst present as a paste at 20° C. A cure inhibitor is dissolved in a solvent compatible with the free radical cure catalyst paste to form an inhibitor solution that is mixed into the paste. A filler composition is also provided that includes an ethylenically unsaturated resin, a crosslinking agent; and the free radical cure catalyst composition. A method of repairing a vehicle body is provided that includes an uncured layer of the composition as noted above is applied to a substrate. The uncured layer is modified during a working time of from 8 to 35 minutes. The uncured layer is allowed to cure under free radical conditions to form a cured layer.