The quick answer is a cement mixer can be used however there are a few points to note. The mixing action may tend to leave resin and hardener on the sides of the mixer which may slightly lessen the strength of the product. The mixer is also very difficult to clean and I would recommend cleaning after every couple of mixes.
A forced action mixer is the best but can be rather expensive.
The paddle mixer and large mixing tub is the simplest but if a large area is being grouted it can become tedious.