I use the chipex paint as it's a good colour match (for the 3 cars I've tried it with, 2 different silvers and 1 red), but then have wet sanded it rather than use the levelling fluid, and more recently I've experimented with a Festool denibber tool that I bought. It all depends how confident you are really and what equipment you have, and possibly whether you can afford to have it fixed properly if you make a mess :lol:
As for the size of the kit, if you're using the levelling fluid, you'll definitely run out of that before paint! The bigger paint kit gives you plenty, if you run out of it you'd have been better off paying for the car respraying. On my old car I did a road rash fix on the skirts which were absolutely battered along the back edge with probably thousands of small chips, smeared paint all over and then wiped off the excess with the levelling fluid, and still have probably 2/3 of the bottle left. From a normal viewing distance (not crouching down to look) you couldn't tell at all, it looked factory fresh, well worth the price