An example of instant Kamma is when you have just said something so stupid that somebody just slapped you in the face. Instant Kamma, yeah, it's real.
Can you burn off bad Kamma? We don't use the words "burn off bad Kamma". Remember the analogy we like to give of drinking salt water from a bathtub. You can certainly dilute down bad Kamma so that it doesn't hurt, but as to burning off bad Kamma, we don't use that way of speaking.
See the results of good Kamma in this life manifest? I am looking at it right now. Take a look in the mirror one day. See the results of your good Kamma. Or, if you don't think you've made any good Kamma, would you rather be the person you were ten years ago? Of course there's results, of course you can see good results, but you have to open your eyes, because a lot of people go, "No, no, no, not me!", and get into self-pity. Reflect on your good past Kamma, and you're going to see the good results more often.