I've been having problems in using Tinfoil and NUT in the past, and so I found that NS-USBloader + Awoo Installer to be a more reliable way.
TLDR:
On Windows:
1. Install Java Runtime Environment (JRE)
2. Download and run NS-USBloader
3. Install drivers in NS-USBloader
4. Open Awoo Installer on your Switch, connect USB cable and select Install over USB
5. Select nsp/nsz to install in NS-USBloader and click Upload to NS
6. On Awoo Installer, select files and install
7. ...
8. Done!