I am not suggesting you need to epoxy your whole floor, just that its not too hard to DIY.
The epoxy product you linked should work fine. It is like a thick putty. If the cracks are wide enough to get sticky silly putty deep into them then that's all you need to do. If the cracks are thin (can you put a credit card into it?) then it will be really hard to get the crack sealer very deep and you will end up spreading more of it on top of your garage floor.
The crack chaser is like a circular saw blade that will make the crack wide enough that it is easy to get the epoxy or other filler into it. My floor had lots of thin cracks that I wanted to patch. I would not have been able to get the crack sealer in deep without opening them up. If you google "crack chaser" you will see its a wheel with a wedge shaped point. I think the smallest was 4" diameter for the wheel. The cheapest one you can find will last plenty long for 1 garage.
An angle grinder is a small hand power tool. For one job you can pick one up pretty cheap at Harbor Freight. This will spin the crack chaser really fast. You do an awkward hunched over walk along the crack with this thing running and it cuts the crack to make it wide and deep enough to get the glue into it. It goes really fast and is surprisingly easy to do. The crack chaser will try and follow the path of the crack like the name suggests. Wear safety glasses and a breathing mask, cause this makes a ton of dust.
The epoxy stuff in your link will be brittle when it dries/hardens. Perfect for cracks in the middle of the floor. My garage had a crack around the edge where the floor meets the wall. To fill that you want a flexible epoxy or a silicone caulk to fill these cracks as they will move slightly.
I had never heard of any of this stuff either before if did my floor this fall.
This had the best instructions I found on the web:
http://allgaragefloors.com/concrete-floor-repair/