Home network help needed

[Booster6]

Hey all, Im a home networking newbie and am looking for some advice.
I have an Asus RT-AC1200GE router, that provides good coverage of my house, most of the time. Sometimes however, laptops and tablets the far corner or the house struggle get a stable connection.
I have tried moving the router to every other viable location in the house, and we have a dead spot no matter what, so the obvious solution is to set up some kind of additional access point or repeater or whatever. This is where we get out of my depth. A friend of mine had an Asus RT-AC56U that he wasnt using so I was hoping to be able to set up a mesh network of some kind, but I cant figure out how. I figured out how to set the second router to AP mode, and create a second network with a different SSID, which would work, but I'd rather not have to manually switch devices between to the 2 networks (Especially since my father who lives with me would not be able to handle that).

So 2 questions I guess:
1) Is there actually a way to get these 2 routers to exist as a mesh network so devices will just switch which they are connected to on their own 
Or failing that
2) Is there a different repeater or something I can buy thats not wildly expensive to achieve what I want?

Thanks in advance for the help and advice

[Lurick]

They should have Asus AI Mesh or something similar in name that allows them to mesh together.

[Bdavis]

If you make the ssids and passwords the same on both routers your devices will automatically switch between the two.