For our particular project you only need to install Nix and then run nix develop, but I'd indeed recommend to use direnv. For me it's not an issue, since I run NixOS on development VMs, but a colleague who was not using Nix before (I think) also wrote a bash script to set up an AWS VM with the NixOS AMI and then rolls out a minimal NixOS configuration.
I think for people who don't want to dive into Nix much, doing an imperative install (nix profile install) of the necessary packages is also fine. You could even make your own small meta-package that depends on everything that is needed. Then they could do a nix profile install yourflake#yourmetapackage and have all the tools they need. But I agree direnv is a bit harder, since you'll have to put something in the shell rc/profile.
I think for people who don't want to dive into Nix much, doing an imperative install (nix profile install) of the necessary packages is also fine. You could even make your own small meta-package that depends on everything that is needed. Then they could do a nix profile install yourflake#yourmetapackage and have all the tools they need. But I agree direnv is a bit harder, since you'll have to put something in the shell rc/profile.