Keep in ind that you will need t heat it once you add the alcohol. A microwave is ideal because it's fast, but use a lower power setting so you don't accidentally overheat it. You would need to heat it pretty high to damage it, but none the less, a microwave at like power level 7 (70% power) is good. Obviously, the amount of alcohol you are heating will determine how long you need to heat it for, but if you have 150 ml of alcohol mixed together with the MK, put it in the microwave at 70% power for 20 seconds. After the 20 seconds is up immediately take it out and swirl it around a bit to see how much it has dissolved and if necessary (likely) put it back in for another 10 seconds and check again. If necessary, continue to repeat in 5-7 second increments until dissolved. By the 2nd time in the microwave--maybe the 3rd--it should be dissolved. Keep in mind that when MK is dissolved in alcohol, it may still look cloudy, not clear. However, once it is added to the carriers (which is the bulk of the product) it will look clear.
If you use enough alcohol it will turn completely clear before adding any carriers, but 190-200 proof alcohol is kind of expensive, so I use the minimum amount required to make it work. You may want to use a little more at first because it will be easier to know when it is dissolved when using larger amounts of alcohol.
If for some reason you can't get the MK to dissolve in alcohol after applying heat, this might mean it has too many fillers/impurities. It doesn't necessarily mean it is dangerous, but it could still contains impurities none the less. If this happens, don't worry. You can always add your carriers (glycerin or PEG) to the alcohol mixture and put the whole thing in the oven at 180 degrees for 45-60 minutes (stir it every 10-15 minutes) ad it will eventually dissolve into a clear solution. In fact, this may be the safest way to ensure you don't accidentally damage the MK through overheating. It is certainly more time consuming this way because you have to wait for the oven to slowly dissolve it (when using a microwave you could be ready to bottle your MK 2 minutes after adding alcohol), but it does work. So, you could just mix the MK and alcohol together, then add the carriers, then put the whole thing in the oven...and it will eventually dissolve. Heat it in the oven in a glass baking pan.