If it is due to a steep swing he probably experiences a lot of tops and chunks also.
I am under the impression a push results from an in-to-out swing and a square clubface (relative to the swing line, not the target).
If what I believe is correct, it seems like you should focus on swinging more out-to-in (but not excessively so).
Try taking three practice swings. In the first, swing normally, in to out. Then have a swing that intentionally goes out to in, the...