While I'm sure someone somewhere gets good results brushing Tamiya, I've never seen it. They're not a true acrylic, they are ether based. That's what makes them so popular, they are almost enamel like, but spray well because the ether evaporates quickly. Great for AB, horrible for hand brushing. I'm sure the make a retarder, it's Tamiya after all.
Honestly, true acrylics like Vallejo, Citadel, Reaper, etc hand brush like a dream. Add some flow improver and retarder and it'll stay workable for hours, paint thin and you can keep a wet edge forever. Add a wet palette and you can spread the project over week or more and still have fresh paint to use (mainly for figure painting where you layer colors).
