For the USAMO/IMO, the ability to solve a single problem is already a large step. Solving 4 out of the 6 problems means you almost surely make the IMO team. I think the issue is more how he can get good enough to solve such difficult problems (they are also proofbased, so an actual solution should always get full points barring a bad writeup).
One core skill is ability to solve problems eventually, to not stop before you solved the problem. Bringing this to contest setting requires speeding up to a level that is probably unattainable because of limitations of raw ability, and might benefit from lots of training. But another failure mode is stopping right after you solve the problem, so that you won’t notice a stupid error, even though you’ve got the solution. This is a piece of low-hanging fruit that doesn’t necessarily require any significant effort (in comparison), but still needs to be collected.
For the USAMO/IMO, the ability to solve a single problem is already a large step. Solving 4 out of the 6 problems means you almost surely make the IMO team. I think the issue is more how he can get good enough to solve such difficult problems (they are also proofbased, so an actual solution should always get full points barring a bad writeup).
One core skill is ability to solve problems eventually, to not stop before you solved the problem. Bringing this to contest setting requires speeding up to a level that is probably unattainable because of limitations of raw ability, and might benefit from lots of training. But another failure mode is stopping right after you solve the problem, so that you won’t notice a stupid error, even though you’ve got the solution. This is a piece of low-hanging fruit that doesn’t necessarily require any significant effort (in comparison), but still needs to be collected.