That's one of those "it depends" things. In general, I'd say I put around 40 drops in 8oz of liquid and layer it until I get the intensity I want. But, I've used as little as just a few drops when I want some shading. I used both mixes in a 1lb mix of SealCoat on the mahogany for my credenza.
For the bed project I hope to get back on sometime in my lifetime, I tested with different amounts of TT in water and decided on 10 drops of TT Brown Mahogany per ounce of water. That gives me the look I want on the red oak. I wipe with a damp rag first, sand the nibs, drift the dye on with a sprayer, and seal with a 1lb mix of SealCoat.