As a carpet cleaner in Tampa FL I highly recommend spot cleaning carpets with vinegar. It's a great cleaning and sanitizing agent, especially with carpets. It's low pH makes it safe to use on most synthetic carpets and it evaporates leaving no sticky residues on the carpet fibers. It works great on water based spills and biological messes, because it not only cleans it also disinfects. I have used vinegar as a go to cleaner in my own home on many occasions.
In this video about spot cleaning carpets with vinegar there are some things the viewer should be aware of. You can use 100% vinegar in a spray bottle to clean messes but I recommend diluting it with water mixed at a 1 to 1 ratio. When I use vinegar to clean I mix it with carbonated water instead, It really amps up the cleaning power. The bubbles in the carbonated water lift the spot right out.
In the video she sprays the solution on to the spot, but she doesn't use nearly enough. Adjusted the spray nozzle until its almost a stream of solution coming out of the bottle. Then spray the spot heavily. Using a scrub brush on your carpet is not advised. You can easily damage the carpet fibers with aggressive scrubbing like she does in the video. Scrubbing carpets is the a cardinal sin in the professional carpet cleaning world. Instead, gently work the solution through the carpet with a plastic knife or rubber spatula, Moving it back and forth to gently massage it into the carpet.
Now here's the toughest part. Wait 30 seconds before cleaning up the cleaning solution. If your spot cleaning carpets with vinegar you have to let it work by giving it some needed dwell time. In the video she aggressively rubs the spot with paper towels to remove the solution. The best way to remove the solution is to use a white cotton towel. Instead of rubbing the spot, gently blot it to soak up the vinegar solution and the spot. After you have soaked up most of it, put down a fresh towel and stand on it for 30 seconds. This will remove the remaining moisture, leaving it fresh and nearly dry.
If you're still have problem removing the spot its time to throw in the towel and call a professional carpet cleaner.