Very confused directions are very small

Okay my son as a toddler accidentally cut his finger nail. He is always afraid of nail clippers so I decided to try this. First you need tons of batteries and I still havent found the right buffer to use on his nails (very thin) . Also it seems like it may not last long by the quality of the product. My son actually likes it . However I am still trying to figure out the 9-1 system so not a pro yet. It still working and using the each of the four heads it comes with. there are blue pink green and grey. so far I believe that the Green is for finner smoothing, pink is for shinning, the blue and the grey seem to work the best on his nails. I also used it on mine and was very happy.