You can take lechitin (Blackmore brand) to break down the blockage during the period of stop pumping/latching on. Also, try to delay pumping gradually instead of sudden stopping. I find it is very useful to use cold cabbage to soothe the engorgement.
Only pump when you feel very full and keep delaying to pump. It took me only 3-4 days to stop pumping totally. Usually I pump 4 hourly at 180ml up till my LO was 16 mths. I would prefer to stop naturally without medications.
delay your pumps.. however before you stop completely.. make sure you got no ducts..
Take 8 cups of peppermint tea a day. :)