Push the weight up as fast as you can, pause to ensure you are not using momentum then lower the weight twice as slow as was lifted, each rep identical cadence to the next, you keep doing this until you cannot move the weight, lower it, do another, lower it, try again, hold it as long as you can, put it down, then go straight to the next exercise and do the same.
I beleive just slowing down the negative ensures you have the rep under control and that there is no momentum being used.