We used the TT with the Enfamil formual. We used the cold milk, but always end up mixing our formula in a larger container. We used a shaker (that you shake cream in) as it held a lot more liquid, and was able to move around more. We roll it in our hands for a few minutes, and then shake vigorously up and down, and then transfer to the bottle. We have not had any lumps since using this.