Firstly have you taken the wire out of the hat? That’s an absolute starter for 10 or you risk looking like a landing pad. This asserts dominance over the hat and should remove any psychological resistance to abandoning the Russian train conductor’s hat shape fairly quickly.
Secondly, it comes down to treating it with absolute contempt at all times. Travelling in the car? Throw it into the passenger footwell. Desk in your office? Launch it at your desk, when it falls of throw it back at the desk, then and only then throw it at the hook on the back of your door.
For peak triangle, tying a belt round it and leaving it in the bathroom whilst you shower will help, steam will do wonders.
Whilst your uniform should always look good the hat is, and always has been, a notable exception. The gasher the hat the better.
I was told once by a regular to put lots of damp newspaper around it on the top of the hat. Then put a belt round it to hold the shape, then leave to dry in the airing cupboard. I haven’t tried it though.
I don’t think the officers’ SD caps from stores, which people tend to use these days, lend themselves to being easily shaped or over time naturally taking on that ‘look’. They appear to be based on airmen’s No 1 hats, which have wire stiffeners in them and which are therefore flat and too rigid in the top. They also have a round headband and nobody’s head is round!
The problem is that I’m not even sure you can buy what I would call ‘traditional’ officers SD caps any more. Grieves & Hawkes ones always looked good but we’re very expensive, but they don’t do uniforms any more, at least not RAF ones and I don’t know what outlets such as Snaiths offer any more. The ‘traditional’ type used to be called a ‘Bates’ I believe and it won’t have a wire stiffener in it, but will have felt on some other soft lining under the top which means that the sides can flop a bit.