Practice this in private. Place the back of your tongue against the roof of your mouth and force a bit of air out in the form of a "kh". The air should come from the space between your tongue and your throat, not deeply from your lungs.

That will do and is preferable to kattan, shattan or chatton, but if you wish to pronounce it as it is natively pronounced in Badenoch, Strathdearn and Strathnairn you must repeat the "kh" sound immediately preceeding the double "t". The result will be khaakhtun.

Rex