When it comes to mixing floor tile mortar, it really is important to get the correct consistency to make your job of laying floor tiles easier. First of all, depending on the subfloor you wish to lay tiles on, you want to choose the appropriate type of floor tile mortar. For breathable subfloors such as plywood, then you will need to apply modified mortar, but for solid concrete floors a standard unmodified mortar will suffice.
If you are not exactly sure on which type you will require for your application however, your local hardware store should point you in the right direction. With regards to brands, I personally have no specific preference on which to recommend, as I have found over the years that they all work as well as the other.
Heavy Duty Drill
Standard floor tile mortar which the professionals use comes in the form of a dry powder which you add water to in order to get the consistency of mud. There are other types available which are pre-mixed and ready to slap straight on to your floor, but I highly recommend that you stay away from these when tiling floors, for reasons I mentioned in a previous article.
To mix the mortar correctly, you really have a choice of only two methods. Either by use of a heavy duty power drill fitted with a mixing paddle, (or an actual mixing drill specifically built for the purpose), or by the good old fashioned method of applied 'elbow grease' using your trowel.
When going with the traditional manual method, this can obviously take some considerable amount of time and effort with an end result of having forearms like 'Popeye'. However, it is still very effective and it's how I personally started out when I first began floor tiling.
If opting for the easier mixing drill method, a simple cheap paint or plaster mixing paddle attachment fitted into the chuck of a drill can do the job ideally, but don't go using any common domestic hand drill. With the amount of drag involved in mixing thick mortar, you can easily fry the motor of a small drill due to excessive friction.
Use only a drill with a minimum of having a 1/2" chuck fitted so you know that the motor has some reasonable amount of power to contend with the drag, and make sure you have at least one side handle for better control over mixing. If ever you are not sure whether your drill can cope with the job, then test it first on small quantities of mortar mix to see how the motor fairs, and just go with your instincts from then on.