Good question. I don't think there is a standard answer to it.
For me, I apply several droplets all over from the front to my crown. Now, the front of my hair is responding, albeit sluggishly, yet the hair at the back of my neck and my beard got noticeably thicker immediately!? So, I think that hairs on some parts of the head respond with only a hint of the substance in your skin, but other hairs (unfortunately, the DHT-affected ones) seem to need more time and patience for minoxidil to do its thing.
I think it varies from person to person. I would doubt that 4 drops would work for the entire head... but for a person who is lucky enough to be a great natural responder to minoxidil, it might. Some people respond to it all over, some people only respond in the crown and not the front, and yet for others minoxidil seems to have no effect.
I suggest experimenting... and watching what happens.
As for the thinning on the right side... I am going out on a limb here, but from my personal experience the right side of the head is naturally weaker. For me, it is the side that was the most thin, and is the side that is taking minoxidil longer to positively affect. I brought this up with my gf's boss, a dermotologist (who is not really a hair specialist, but he knows quite a bit) and he says it has to do with the fact that hair grows on your head in a spiral pattern.
If minoxidil starts to work for you as it does for me, the first positive sign you will notice is a thickening of the thin, but existing hairs. Regrowth, i.e. an actual increase in hair count, takes more time.