first off you should fuck off the black t-cut and the autoglym! both imo are crap. both are full of baulking agents which are chalk. these dust up and on a black cr you will be chasing dust forever!!
i own a gloss black car and its THE hardest colour to keep looking good.it scratches easy amd shows any imperfection.

if it is covered in swirls you need to address this rather than mask it with poor product. 95 percent of swirls an scratches come from washing.if you use a sponge bin it!a good wash mitt is the best item.and either use the two bucket method(one with clean water in to rinse the mitt in and the other with shampoo in),or use a bucket with a gritguard so it traps the grit at the bottom of the bucket(i use tow buckets both with grit guards). and imo to dry you should be using a drying towel/watermagnet as these are softer and also dont dry and crack and remove less wax from the car.
i would first start by claying the car to remove any bonded contaminents like tree sap,bird lime etc.
to address your swirls you can either use a dual action polisher(meguiars g220 v2 is awesome) or you can do by hand if you dont have access to a polisher.
either way you can use meguiars ultimate compound to do this.it will safely remove them leaving a swirl free finish ready for you to polish.
i then use meguairs show car glaze pure polish(no bulking agents so no dust)being pure means less product is used and this will "mosturise"the paint deepening the colour.
then i seal it in with a good quality wax, i use meguiars number 26 high tech yellow wax. its a high carnuba content wax which is easy to use and gives a great finish and lasts.
then you will find you have to only wax it even now an then rather than trying to polish and hide the issue you have like you were before.
hope this helps.any questions feel free to ask,pm if you like