Gerke Hoekstra is very experienced in lead rope solo climbing and tope rope solo climbing. I’ve been using these techniques and I love the freedom it gives me: I can work out the beta of a hard sport climbing route or climb laps on an easy route by myself and work on endurance.
Gerke shows is preferred method using a petzl grigri, petzl asap and petzl microtraxion, but he also shows a cheaper system using only the petzl grigri and backup knots.
Disclaimer: rope solo is dangerous, and none of these devices are designed for it! One thing that isn’t discussed is the factor 2 fall which can occur in multipitch climbing. A factor 2 fall can result in a force of 6kN and is VERY dangerous. Best thing to do is to avoid factor 2 falls. Risk management is something you should be able to do when multipitch climbing.
Other resources:
Andy Kirkpatrick:
Petzl: