I used this one and it works great
https://www.amazon.com/Maxpower-Planet-Pet-Grooming-Brush/dp/B07P2N8HQH/ref=sr_1_2?hvadid=598848382939&hvdev=c&hvlocphy=9052182&hvnetw=g&hvqmt=e&hvrand=15874390817158552180&hvtargid=kwd-1392759795564&hydadcr=648_1015024273&keywords=undercoat+rake+comb+for+dogs&qid=1682885661&sr=8-2
I have two aussies one with a thin wiry coat and one with the fluffiest ever. I use an under coat rake a few times a month https://www.amazon.com/dp/B07P2N8HQH?psc=1&ref=ppx_yo2_dt_b_product_details and a regular brush with fine teeth like a slicker brush that is purple on amazon.
They will break every two years but good set up for $20.
Those double sided brushes are garbage in my opinion. I'll link a few things I've bought from Amazon to use on my dog at home. Brushes are going to depend on the coat of your dog.
Undercoat rake - this is the exact one I have. Used on both a corgi and a border collie mix
long pin slicker brush (they come in different pin lengths. I like this one, I use an Artero at work though.