Kyalami specifically is a bit of a challenge, it's pricey, and they don't have weekly/monthly open track days like Zwartkops does.
If you have the budget to hire the track out all by yourself or with a group of friends then its easy of course. Not sure what this costs these days, enquired about this years ago but it was way too much, R50,000 for the day or something stupid like that, wouldn't be surprised if it's much more than that now.
Otherwise you will have to wait for a club to organise a track day and join that.
Next BMW Club track day is this Sunday actually.
MSA license will cost you around R600 (annual)
BMW Club membership R350 (annual)
Time trial entry R850
Check out
www.bmwcarclub.co.za for specifics.
You can also browse the other car forums to see what they are doing, last I was on Kyalami was with the VW Club, awesome day, and cheaper than the BMW guys.
I'd say the Zwartkops monthly Super Trax days are your best bet. Everything you need is on
www.zwartkops.co.za
Cheers