Rusty Pilot Refreshers are generally customized for the needs of the pilot. In theory, all that is needed for a rusty pilot to be legal to fly again is a flight review, (requires a minimum of one hour of flight training and one hour of ground). However, studies have found that on average a rusty pilot needs an additional 45 minutes of training for each year of rust to regain flight proficiency and become familiar with any regulatory changes (such as ADS-B requirements and airspace changes).
AOPA has a great guide for rusty pilots here: https://www.aopa.org/-/media/Files/AOPA/Home/Training-and-Safety/Rusty-Pilots/rustypilotsresourceguide.pdf
The Sport Pilot training center has a good guide to “downgrading” to Sport Pilot privleges here: https://sportpilottraining.sportaviationcenter.com/downgrade-transition-lsa/
Many rusty pilots ask about operating under Sport Pilot Rules. There is no checkride needed. Any “higher” level pilot certificate (i.e. Recreational, Private, Commercial, or ATP) can legally operate under Sport Pilot rules (with a flight review and valid driver’s license, and if they have not had a medical denied or revoked). Transition training is a must as LSAs often have unique characteristics that might be unexpected.
One attractive feature of Sport Pilot is for a pilot to add another rating to Sport pilots with only a proficiency check with a CFI instead of a checkride with a DPE. For example, a Private/Commercial/ATP pilot might choose to add a Sport Pilot seaplane rating with a proficiency check.
The FAA Mosaic initiative includes potential changes to Sport Pilot rules. The FAA has stated these changes will be announced in August 2023 during Air Venture. Changes are expected to include an expansion of aircraft that are “Sport Pilot” eligible. As the regs exist today, Sport Pilots can fly LSA/LSX aircraft and many experimental and legacy aircraft that match the performance numbers of LSA (Piper Cubs, Taylorcraft, and many others). There are indications that common trainers such as Piper PA-28 Cherokees, Cessna 152/172 may be sport pilot eligible in the future, making Sport Pilot more attractive to rusty pilots.
This article discussions the potential changes: https://bydanjohnson.com/midwest-2021-day-1-update-about-faas-mosaic-regulation-then-flying-the-fusion-chasing-the-fox/