You have to remove the hub assy,brake assy,stub axle assy,and the swivel assy to get at the large swivel seal.It's not that big of a job but it will take a little time.While you have it apart you might as well replace the hub seals.Of course in my experience the leak will stop for a while(just long enough to make you think it's stopped for good).Hope this helps.
sounds to me like your swivel seals have seen better days,quickest fix is to buy swivel grease its a semi fluid ep grease,my rangie used to leak used the swivel grease and its all still in there.
First check the condition of your chromes if the are pitted or flaky,you will be wasting your time putting new seals in they will get chewed up and start leaking in no time new chromes will be required to seal properly.
I wouldn't go the grease route, if the greae gets contaminated, which it will, there is no way to drain and replace. I have also replaced my swivel pin seals and drain and replace the oil every time I do an oil change. It's not that big a deal.
I have had grease in mine for 3 years with no problems whatsoever no contamination,I do a lot of Beach driving so the swivels are in a very harsh enviroment as yet I have had no Bearing of CV failures.And the grease is fluid enough to drain,its not an awful lot thicker than E.P. oil.
Most of the guys down here (South Africa) recommend using CV joint grease, which is much thicker than what you say you are using. If you can drain it, then it should be fine.
I do a lot of driving in water and thick mud, so my swivel pin oil (EP90) gets contaminated all the time. It's probably best if it does leak so that I constantly top up with clean oil, thereby keeping it all a bit cleaner.
I have used 1-shot grease for years on my 109- When I finally did replace the swivel seals, the innards were in great shape.
If your oil leak has gotten into the brakes, it's not a swivel seal that's gone but a hub seal. This is a rubber seal that sits inside the inner side of the hub, immediately inboard of the inner wheel bearings, preventing oil leaking from the svivel housing and hub assy into the brake assy.
To replace it, you need to remove the wheel, drive flange, outer wheel bearings and hub. Check the stub axles for wear on the seal face and bearing locations. Any wear on this also means replacement (expensive).
While you're replacing the seal, I'd replace the bearings too. The Gen Parts kit costs £15 and has both brgs, hub seal, drive flange gasket, hub nut lock washer (the big one), hub cap and o-ring.
If the shoes have been contaminated, replace them too and clean the drums carefully.
While you're doing all this, you can also bleed the front brakes (109 dual line) perfectly by removing the backplate from the swivel housing, and bleeding with the plate held horizontally with pipe work upwards. Refit the brakes, followed by the hub, and at the end you'll notice significantly sharper brakes. Aloow a day to complete both sides at a leisurely pace.