When can I use post-game quick chat in Rocket League?

After a game of Rocket League, I am having trouble using the post-game quick chat (such as "gg", "well played", etc.). I either seem to press the hotkeys before the quick chat options have switched to post-game, so I end up with the in-game options (e.g. "What a save!"), or I press the hotkeys too late, with nothing appearing at all.

When I am too early, I wait until the quick chat menu fades out without selecting anything, at which point I try again, but the in-game options keep appearing. Eventually the game no longer accepts input without ever providing any post-game chat options. Does doing this cause the in-game options to persist longer than they would if I had just waited the correct time?

Is there a "sweet spot" at which point I can safely use the post-game quick chat? Can I time it to any messages or screen changes in the game?

In case it matters, I am playing through Steam on Windows 10 and using an XBOX 360 controller with the USB wireless dongle.

Here's the progression after each game:

Post-game goal replay (if any): Can quickchat, but not say 'gg'
"Winners" overlay: Can say gg
Winners celebration dance: Can say gg
Experience bar overlay: Can't say anything
Item unlocks: Can't say anything
Post-game: Can't quick-chat, but can still type messages. However, only people on the same platform as you (or in your party) can read typed messages.

So the "sweet spot" is after the winner is official announced, but before the endgame celebration has completed.