Just curious, what type of angora do you have? I have a french angora.
I just use a cat brush I got at walmart, which is a slicker I think. As long as you are gentle and don’t scrape/scratch their skin with it it should be fine.
For the mats around his chin, try and work it out with your fingers/comb if he’ll let you. But if they are too bad/he won’t let you the vets might be willing to do it for you.
As for the pineapple, I know A LOT of people/angora breeders over where I live give their angoras a pineapple chunk a day, although I am not sure it really works like they say it does. I sometimes give my bun pineapple because she LOVES it, although I haven’t noticed any particular help with preventing wool block with it. But keep in mind if you are giving a chunk of pineapple a day to your bun that should be the only fruit/sugary food they consume a day. Although I would make it more occasional like a couple times a week or for special occasions. Too much sugar can cause health problems like diabetes. Good luck!
<3