So for those who don't know what ACISS DP1 is like (or has been recently from what I'm told), they treat getting your cap badge at the end of the course as a huge deal. You're stuck wearing a cornflake up until that point.
During the course, I tried messing with my beret to make it look better. I had already cut out the liner, which instantly made it look better. I tried it with a trench, no trench, pulled as tight as possible, increasing/decreasing the fold on the side etc. My method of forming, which works well in my experience, is putting my beret upside-down in the sink and filling it with hot water until my beret (not the sink) is completely full of water, then wringing it out, forming it, and wearing it for a couple hours. Usually it will start drying in this time. When I'm about to go to bed I'll put it on a lamp or something so it doesn't look "wrinkled" from drying while folded.
The look I ended up going for is minimal-no trench, pulled tight with a small fold on the side. Rather than a straight horizontal line above my eyebrows when I'm wearing it, I have it just barely touching my right eyebrow with it a couple cm above my left eyebrow. I find it has a very "deliberate" look to it. Looks best right after a haircut.