We actually did this at our home track. Got a few dump loads of sand, spread it out in our corners, and tilled it in. Our track isn't big, I would compare it to slightly larger than arena cross size, and it made little to no difference. I think you would need a lot of sand to really loosen up the dirt so it doesn't hard pack as much.

Mixing hard pack track soil with sand can be a smart move to make it more manageable. It's not too tough of a job if you've got the right equipment, like a tractor or soil tiller.
But before you dive in, it's a good idea to get the soil tested. You should check out Soil Testing Brisbane – they can give you insights into your soil's composition and what kind of sand mix might work best. It's all about finding that sweet spot to make your track just right for your needs.
When it comes to the actual mixing, it can be a bit of a workout, but it's doable. Start with small sections to see how the mix behaves, and adjust as needed.