A personal experience using a Gestor:
I’ve just upgraded my thin green residence card to a TIE. Used Assesoria Zamora in town. They smooth the way very well. They arranged the CITA’s and did all the paperwork which they forwarded to the TH and to the CNP in Murcia.
I had a 09:45 appointment with the Padron but went early. The security guy put me in front of the queue and the lady at the Padron counter was very nice. At the CNP headquarters in Murcia you punch your NIE number in and I got a ticket marked with “UK” and a number. I noticed French people get tickets with F, Moroccans with M and so forth. It seems that various counters are reserved to handle various nationalities.
The guy I had was very nice but only spoke Spanish. Maybe this was because I spoke Spanish. I don’t know. In any event, he had the paperwork and photos forwarded by Zamora and all I had to do was to pass over my passport and green card and give digital prints of both forefingers. Took only 8 minutes comprising 3 minutes waiting and 5 minutes at desk.
You pay Zamora € 49 plus €12 for the complete process. Zamora will now arrange my CITA in 4 weeks time when I will return to the CNP hand over my green card and collect my digitised TIE.
Easy peasy in fact.