It's almost impossible to not get dirt, bugs, or some sort of texture in your final paint. Color sanding and buffing is the method used to remove the imperfections in your final job. This process can be used on all clearcoat jobs and most single stage paints that are solid colors. Color sanding single stage metallics runs the risk of smearing the metallics. Although a light color sanding and buffing may be fine.
Start by choosing which grit of paper you would like to sand with. Finer grits will take longer to sand but will buff easier. Coarser grits cut fast but may take a long time to buff. Most pros start with a coarser grit and then sand again with a finer grit. Another reason to start with the coarser grit is because it levels the surface better. It creates a flatter surface where finer grits glide across the defect and smooth them without flattening. In any event, most use 1000 to 100 grit to start and finish with 1500 to 2000.
You'll need a soft or semi-soft sanding block, a pail of very clean water, soap, and a rag. Fill the pail with water and put in a little soap. Here I'm using a hotel liquid soap packet. Put your sandpaper in the water and let it soak for 15 to 20 minutes. Start sanding using the coarser grit by wrapping the paper around your block. Lightly sand the surface of the paint as to remove the irregularities. Be extremely cautious here, you can sand through and destroy the whole job. Check the surface regularly by drying it to see how far you've gone. A squeegee works well to help dry the surface. If you're going for the show car shine, you need to remove all the imperfections but don't sand any farther. If you just want to clean it up, just lightly sand the tops of the irregularities off. This will leave a texture but no big lumps or dirt. Much like a factory paint job. Be wary not to sand much on corners or edges. If you are concerned, put some masking tape over areas you don't want to sand though. Do not color sand in any area that you can't get into with a buffing wheel.
In the pictures, you can see where I've sanded (the dull spots). The shiny spots are low areas. For a show smooth shine, you want it all to be dull and leveled down to the low spots. In this case I want the part to appear like a factory finish so I will just sand a little more using the finer grit. In this case I'm using 1200 and 200. This finish is very fresh with only about 12 hours since I painted it. This makes it easier to sand but also easier to sand through.
Once the topcoat is sanded to your satisfaction, it's time to polish. You'll need some compounding and polishing pads, a buffer, and some compound and glaze. I use a Makita variable speed unit, as it's easier to control the pad. Allot of pad and compound choice is personal preference. I use a wool pad to start and 3M Perfect-it III Extra Cut Rubbing Compound. The idea here is to remove the sanding scratches and achieve a high gloss. Use the buffer at low speed and let the compound do the work. Try not to push too much. Keep the pad moving and stay away from edges as you can burn through. As the compound starts dissipating, watch the surface of the paint at an angle such that you can see any scratches. Buff until they are gone and all that is left is haze from the compound and pad. Then I'll normally switch to a soft foam polishing pad but stick with the same compound. Working the surface with this should produce glass like results. Anything you can still see in the paint when done with this step will still be visible when you are done. So get it all out. If you have to go back to the wool pad, do it. The final step is to glaze the surface. This is basically like waxing only it won't seal your new paint. Apply the glaze using the same technique with a soft pad. I use Perfect-it III Machine Glaze. When your paint is fully glazed, wash the area with clean water and dry thouroughly with a very clean SOFT cloth.
That's it, now stare at the shine for a while.