All I do is just start the radio feed, then you’ll quickly see that the TV is about 15-30sec ahead (typically although it can be as much as almost a minute). So you watch the play, and un-pause it as Bill’s play by play or the sounds matches the game.
Depending on the venue, sometimes you can hear the ball hit the rim on a FT, or usually you can hear the refs whistle on a foul or OB. So the absolute easiest way I find is to:
Turn the radio down
watch the TV and pause it when the ref blows a whistle
then mute TV, turn up the radio/app
then push play when you hear the whistle on the radio.
The downside to that method is you may have to watch for a bit until a whistle happens, but usually it doesn’t take long.
Football is much easier than basketball due to the amount of stoppage. It’s easy to sync on the refs whistle at the end of any given play. I’ve been listening to KFAN for Vikings and ESPN700 for Utes for probably going on a decade if not more.
Utah @ 
Houston 
.
