I wouldI suggest getting a .001 g scale like the GEM20 from Amazon or Ebay. It will be key while tapering if you use the dry method.
I would start with a small cut, maybe 5% for a couple weeks or so to "test the waters." I use a metal nail file to shave my tablets. To figure out the amount to shave, convert the percentage to decimal format. So if you were to want to reduce by 5%, you would use .05 and multiply that and the total daily weight of your tablets.
In your case it would be the total current weight of the three 1 mg tablets you take.
This is where you'd need a scale to weigh your tablets.
Since you are starting with a relatively large amount of K, you probably can continue your tapering reduction by 10%. Still, you want to be guided by your symptoms and hold longer or make smaller cuts if symptoms are too rough.
I'm tapering clonazepam, so reviewing my signature may give you a good idea for a flexible tapering plan.