I agree with dicksewerrat and would add the following comments:
1. Acid etching is most commonly done with a weak solution of sulfuric acid, but another choice, slightly less dangerous to work with, is phosphoric acid. In either case you must thourghly flush the surface afterward to get rid of any residual acid. This is a good method when there is a lot of grease or oil on the existing floor.
2. An alternative to acid etching is to shot blast the floor. There are a number of firms the do this commercially. This is a good method when there is a lot of paint on the floor. One major advantage is there are no disposal problems of liquid acid wastewater. The shot blasters have a dust collector attached and vaccum up the shot when they are done. They do have to dispose of the dust residue, which can be considerable, but it can go to a normal landfill.
3. A final alternative is to use a terrazzo grinder to take off the top surface. There is no dust and the floor can be shop vac'd clean and residue disposed of in a landfill. This can give a really nice finished floor finish and if you need to be slip resistant add silica sand to the new coating.
In all of the above cases, the it is illegal to dump the residue down a sewer! Tape the floor drains with duct tape while working.
As far as bonding agents for a thin concrete topping, the cement slurry is quick and easy. Other methods are a laytex bonding agent like Acril 60 or an epoxy bonding agent, each getting progressively more expensive. The choice depends on the condition of the original floor slab and budget.
Just painting floor with some coating product is generally not good because some of these floors don't have a vapor barrier under them and the coating can be lifted off by water vapor pressure transmitted through the slab.
Just a few more things to think about! Good luck.
