Can I block the time between reservations for resource refuel/cleaning etc.?

Yes, you can set the duration of time blocking in the resource settings.

Let's imagine that you set this duration to 1 hour. In this case, each booking visible on the customer's calendar will start 1 hour earlier and end 1 hour later. This will prevent the customer from booking the resource at the time of the intended preparation (refuel, cleaning etc.). This guarantees a 1-hour interval between bookings.