maguiars

Just purchased one of these and found it hard not to leave water marks. Its there a nack to using these? Also clayed my car for the first time, using mags quick detailer, I seam to use quite a bit of the spray, can I just use water when this runs out as I think the spray will be gone before...

Will maguiars quick clay remoove the wax that is already on the car, ie will I have to polish then wax after I use the clay? Also di I dry the car before using the clay after shampooing or do I leave wet and the spray and clay? Many thanks