What software did you use to do that? Years ago I set something similiar up with an Ubuntu distro but never got it to work quite right.
I did not use any special software. You just need two USB sticks. Let me call them USB1 and USB2.
You can use USB1 to write the Devuan .iso or .img file via the dd command. I did this from FreeBSD. You can also do this from Linux with dd, or from windows with balenaEtcher. Then plug the two USB sticks into your PC and boot the one that has Devuan installed on it (USB1).
After that you just have to do the installation as usual. Via GParted I checked the location of the USB on which I wanted to install Devuan (USB2). This turned out to be /dev/sdc so I created a SWAP partition and an EXT4 partition on /dev/sdc and told the installer to install the system there. I also chose MBR instead of GPT because it makes installing Devuan easier. And then I redirected GRUB to use this MBR from /dev/sdc.
Devuan is considered unsuitable for novice Linux users, and many people find Devuan unsuitable for intermediate Linux users as well. Once installed it is as easy as Debian. If you want to make the boot really snappy on an extremely slow USB 2.0 flash stick, you should choose a distro that doesn't use systemd, unless it's Clear Linux. Clear Linux has extremely optimized systemd making it much faster than on 90% of Linux distros. Clear Linux is easy to install and can therefore be placed on a USB stick. You must have 20GB of free space on the USB for Clear Linux. With Devuan you only need something like 11GB. Artix Linux and Void Linux also start quickly from a USB stick, but are not 'super easy' for beginners either. Clear Linux and MX Linux are ultimately super easy to use with a slow USB 2.0 stick for running permanent Linux distro installations that are rather snappy to use and also fast to boot.