The only posts the RN struggled to fill were the QFI slots.
Why? Because as Engines has said, the RN SHAR Squadron set up was different and did not include the requirement for a QFI on 800 or 801. It then took a long period of time to "grow" a QFI , front line tour, Linton /Valley for a tour then back for another year or so on the Harrier before C to I.
The RAF bent over backwards to allow RN aircrew through the system at a faster proportional rate than RAF aircrew
RN students entered the OCU at the same time as their RAF counterparts and finished at the same time on courses that were 50/50 split RN RAF.
The RN even had to recruit ex-RAF aircrew who had failed to gain a single seat recommendation for Typhoon, thus seeing an opportunity to go single seat through the FAA
Not withstanding the fact that pilots at the time of the Harrier would have been in need of a single seat recommendation for Harrier and not Typhoon, the pilots "recruited" by the RN were;
An RAF QWI (already Harrier Qualified)
Two RAF QFIs (already Harrier Qualified)
An Ex Jag Pilot (had left the RAF and rejoined the RN)
An ex GR1 Pilot and QFI who had spent many years at Valley (did not pass 20 Sqn)
An ex GR4 Pilot (did not start/complete 20 Sqn due to the closure of the Harrier)
Yes, the RN were in need of QFIs on the GR7/9.
Don't forget that the RN also had Squadron execs on IV(AC) and 1(F) as well as junior pilots and engineers, just as 800 had RAF pilots.