OK mackerel are the same all over the world the little blue guys. After a couple of turns at them I can tell what I learnt. Leave them whole,well cleaned sure but dont fillet. My brine is basic.Salt ,brown sugar water,dried orange peel 1 or 2 oranges chopped ,coriander seed bay leaf THEN beer.So if I make 4litres I add 1 litre beer.
Next dont brine them too long ,maybe 2 hours .Critically take them out & hang them up for an hour to drain.Then on racks in fridge overnight to form pellicle.
I tie mine in pairs by the tail & hang them head down in MES,found this a better option all round.
I smoke mine for an hour at 70c over hickory + I put the amzps in the MES at same time for extra smoke. I check them at 1 hour,if the juices are running down in drip tray I bump them to 80c check them after 30 mins.If they look done(eyes white) they are.If the heads come off they are overdone. Get them out to cool dont leave them in MES they keep cooking & go mushy.
I posted a thread on this which I am sure you can find quick enough & an old African recipe for smoked mackeral & black eyed peas if that works for you. Good luck.