It seems anyone and everyone in this neighborhood has the agility to metamorphose into a guide. Qualified guides are available near the ticket counter.
Try to avoid the unauthorized 'guides' who pester the visitors the moment one gets down from the bus. These tout-cum-guides are highly active around the Jami Masjid area and the road leading to it.
If you are so needed a guide, fix up the rate and itinerary up front. Also make it clear that you need only guide service to the monuments and nothing else ( like hotel booking, souvenir shopping , donation for a charity and so on... ).
The qualified guides doesn't move around like a tout, nor are they pushy. Typically they approach as you buy ticket and enter the monument. Hire a guide for an hour or so in the palace complex for a quick tour.
Pay and release the guide after a tour. Now you can spend your time re visiting the spots again at your leisure. That is the best strategy especially if you wants to relax and see things at your own pace.
By the way it is worth hiring a guide. More so if you are new to the whole gamut of Mugal history and architecture.