Sorry to hear that you are having these sorts of problems.
You do not say when you had your surgery and this might be relevant because mucus buildup in the anal stump is quite common soon after this type of surgery.
I had some painful, disgusting and seemingly irresolvable problems like this for about a year after surgeryand having tried all sorts of things to resolve the issue, such as digital extraction, suppositories, anal irrigation with the cone, nothing seemed to be working. Eventually, I made a gadget( or rather two gadgets becasue one did not do the job properly).
These were made from anal catheters that I had been using prior to the operation; I adapted them so that they fitted onto the shower in the bath, which gave me enough pressure to force the mucus from the end and sides of the anl stump without causing damage to the tissue. The technique which worked best was to first use the catheter with the end cut off ( and shaped) so that the water shot straight out of the end and cleaned the top end of the stump; I then changed the catheter for the original design which shoots the water out of the sides. Pushing the catheter up the stump and gradually pulling it back out with a twisting round and round movement, dislodged the mucus from the side walls of the anus and forced it out.
Disgusting as it may seem, it gave me great satisfaction to see all that gunge floating down the bath, knowing that it was no longer inside me! It also educated me into seeing what was causing my pain. After about 6-9 months, the mucus started to become clear, runny and odourless , rather than the disgusting, smelly, semi-solid, multi-colours it had been before. Once it had settled down to the clear output I slowed down and then stopped the irrigation and just used incontinence pads to catch the output and I am still doing that today.
I will pass on the very appropriate warning that the nurses conveyed to me when I wanted to try this method for the first time: There are very real dangers in poking catheters up your anus where you can easily puncture the lining of the colon and then you are in real trouble. This danger is greater because there are few nerve cells in that region to let you know when you are causing pain. In my case, the surgeon was not prepared to say how much anal stump there was left, so I was guessing as to where the end of it was. This was why I used the water pressure to do the work, so that it was less likely to puncture the tissue.
I do empathise with you plight in dealing with this matter and I am convinced that the medical profession ought to be giving you appropriate advice and practical help to resolve it.
The method I used has its dangers and I would not recommend it to anyone else as a DIY process. However, If you could find a medic that would do the irrigation for you or at least help you for the first few times, I would be glad to pass on the design of the apparatus that might be able to assist them in their endeavours.