I don't get the attitude that farrier's can't do a good barefoot trim. The farrier has gone to school and understands the whole leg and it's dynamics as well as any veterinarian. Many of the barefoot trimmers have taken very short courses and hang out a shingle.
Saddle, I can extremely well understand that attitude, as no, IME, so many farriers DO NOT have a very good understanding of hoof function, let alone the whole leg & horse, even the ones that have 'gone to school' to learn - I suspect they learn vastly more about blacksmithing & applying shoes than anything else (& in my country as in yours, it's an unregulated industry) so while I agree that there are many little educated/skilled trimmers out there, there are just as many bad farriers. A *good* farrier will do just as good a job as a *good* trimmer, but that's the catch - finding someone, whatever their lable - that truly knows what they're on about! At present, farrier qualifications mean diddly squat IMO & at least a couple of the *good* farriers I know have not been to 'school'. Trimmer 'qualifications' also frequently mean very little(although this seems to be changing & there are a few excellent, comprehensive courses around the world now) and I wouldn't employ anyone without some case studies to look at first at least.
I know it will take a while for his feet to grow out and have a proper trim, but how long do you suspect it will take? Once I find a farrier (and I will be keeping an EXTREMELY close eye on his feet from here on out), how will I go about getting the foot corrected? How long (approximately) will it take for his feet to be fixed? Should he be getting any exercise right now with his feet being in such bad condition?
OP, how long will it take me to lose enough weight & get myself really fit? That's the sort of question you're asking above I'm afraid. There are just too many factors to possibly give you a reasonable answer. If his feet are largely healthy & sound underneath that mess, they will be quicker to recover than if there are underlying/chronic problems. If you find a good trimmer & get the horse well & frequently trimmed, this will be quicker than if you find a dud, one that does only an average job &/or you don't have them done frequently enough to keep them in good shape. If your horse has a metabolic/dietary/systemic problem that's affecting his hooves, you will need to treat/correct that, if you're able, or there may be little improvement regardless of the rest. If your horse's environment/lifestyle is unhealthy for him & his hooves, it will take longer/forever to substantially change his hoof health.
So... I'd forget about the question of 'how long' & concentrate on what you can do to improve the situation. No 1 is good regular trimming. No. 2 is attention to diet & overall health. No. 3 is padding/protecting the hooves if/as needed to allow *comfortable* exercise...