Firstly, after a couple of attempts, I discovered that the only way to allow the icing sugar to properly coat the cookie whilst it bakes, is to roll the cookie dough first in caster sugar, and then roll it liberally (and I mean liberally) in icing sugar. The caster sugar creates a barrier between the cookie and the icing sugar, so that once the cookie is baked, the icing sugar will remain white, and not "melt" onto the cookie, creating a marbling effect which looks more grey than white. So my advice is:
1. coat the cookies in caster sugar first, and then
2. coat them liberally in icing sugar before placing onto the baking tray
The quantities for the sugar "coatings" I have used in the recipe are more than you actually need, but I would rather you have more than less so that you don't run short.
To get all the mix out from the TM bowl, Turbo x 1 second to dislodge the mix from the blades, then scrape around the bowl with a flexible silicon spatula dipped in water (the mix is less inclined to stick to a wet spatula).
After removing the mix, clean your TM bowl by filling the bowl with tap water to just above the centre of the blade shaft, add a very light dollop of detergent, then heat 1 minute / 60 degrees / speed 6 ... remove the lid, and pour the water out and your bowl should be relatively clean.