I definitely think you can increase your ability to 'see the answer'. I was doing a lot of maths problem solving in year 8, and although I didn't do as well on the Westpac as I'd hoped (I'd made something like one mistake on the past paper we did for practise, but then I only got a HD + a prudence award, which is still good in the scheme of things... in my opinion), I was able to solve problems quickly and accurately. Then in year 9 maths at school seemed to be a lot more formulaic, and I wasn't able to problem solve as effectively anymore. I know it doesn't affect others to the same degree as me, but it truly did make a significant difference in my case.
I also know that in physics, it's quite similar. My problem solving skills improved dramatically over the summer school: I was exposed to questions much harder than the NQE, I saw a variety of questions, and most importantly, I did a lot of them. I would be verryyy surprised if someone who attended the summer school one year (for maths of a science) didn't make it again the next (if they were eligible) - you improve so much with experiences like those.
Edit: Just clearing things up, I don't usually do well in the AMC. Each year it's invariably my worst competition result, possibly due to my laziness with the questions, but even so, I'm not a guru at all when it comes to maths competitions.