My dough whisk, Vera, is one of the most useful utensils in my kitchen. There's something magical about the loops that cause whatever you're mixing to combine easier and faster than using a spoon.
Not to be confused with a wire whisk, a dough whisk won't whip very much air into the mixture — unless you want it to. For making your shortbread, operate it just long enough to combine the ingredients, but not so long that it starts kneading the dough.
After mixing, the dough whisk will do a superior job of scraping down your mixing bowl. It requires no electricity, takes up less storage space, and cleanup is a breeze compared to other kinds of mixers. They're so inexpensive, no kitchen should be without one. If you've never tried using a dough whisk, you don't know what you're missing!
Oh, and don't let the name dough whisk fool you. Just as an egg beater can beat things other than eggs, a dough whisk can be used for many things besides dough. Beating eggs, for example; it's so lightweight and balanced that you can flick it rapidly, whisking in air much like a traditional wire whisk, to create a fluffy mixture.
A dough whisk can simplify your kitchen and cooking workflow by replacing several other, bulkier, harder-to-clean utensils. There are many to choose from on Amazon, but they're essentially the same except for size:
My Vera is the larger 14" size, she sells for less than $8. I bought a second whisk which also claimed to be "large", but as you can see, is somewhat smaller. They both work great!