I dunno if this is a proper way... However I remember I did a similar thing to route all my traffic from all my devices to protonVPN's free tier.

I can't remember exactly how, but IIRC 2 wg connections where used (wg0 and wg-ext) and with some iptables rules I was able to route all traffic from wg0 to wg-ext without issues.

While I can't exactly remember how, I think I still have the config files arround if you're interested I can dig into my old backups :)