I always buy the Dr Colourchip ones. 100% colour match and you don't get blobs as you get alcohol with it that means that you wipe all the excess paint from the clear coat surrounding the chip, but the paint itself remains in the chip itself untouched.
It is the only product with which I have not made a mess of it (read you can do it 10 times without worrying, you can always wipe it of again )