If you don't have any brown sugar and need some for a recipe you can make it yourself by mixing granulated sugar and molasses. The best part is that by making brown sugar as needed that you won't need to find tricks to keep it soft or de-clump your brown sugar brick.
Baking weblog Joy the Baker offers the admitted simple recipe for brown sugar. You only need a bowl and a fork for this process but if you need an excuse to use your new mixer it'll work too. The basic ratio you're looking for is one tablespoon of molasses per cup of granulated cane sugar. For the first minute or so of mixing you'll think it won't work, but eventually it'll turn into familiar brown sugar.
How to Make Brown Sugar [Joy the Baker]