CAn you use the smaller one that is meant for the dash on the outside of the car too? I mean it's the same thing only smaller right?

 

A few things - yes, you can use the small one outside (it's the same) but the big one is "puffy" enough I don't see the need.

The $10 two pack at Costco isn't a knockoff - it's just a good deal. They work great on a clean (and more importantly, waxed) car. The technique is be LIGHT. Take big swipes across the car, but you should just be letting the little strings touch the paint, not dragging the weight of the duster across it. If it's loose dust or pollen or anything, it will get picked up. You can shake it out if you think it's getting dirty, but it's supposed to work even better when it's been used a while.

Also, DON'T wash the duster ever. It says not to in the instructions. It's coated in paraffin wax and if you wash it, you lose the coating and it stops working. If you have problems with it after a few years, I think it's time to buy a new one. I love mine though - no scratches at all.

 

I use quick detail spray + 2 microfiber cloths (one to wipe, one to quick buff) to get dust off my car. Takes about 9 minutes to do the whole car and it looks great.