Remember some stories that coaches wouldn't let the players leave the practice court until they made 10 free throws in a row. I guess Coach doesn't use that tactic. Maybe start in smaller increments. 2 or 3 in a row. Also use to be a guy that made 100+ in a row. Thought he worked with some teams 30 years ago. Got to do something to improve the percentage. Takes the wind out of the sails. Sometimes you are praying for 1 out of two.
A lot of coaches run practices in stations. A lot of players can make free throws in succession, and you've probably seen stations where during practice guys go to a station to shoot 2 FTs to simulate a game situation. While you can work on form, and repetition means a lot, a lot of it comes down to what's between your ears when you step to the line in a game situation, which is why FTs down the stretch are increasingly more difficult to hit.
There are stories that Wilt Chamberlain would routinely take money from other Lakers, including Jerry West, in practice by outshooting them from the FT line. Chamberlain of course, was one of the worst FT shooters in history.
Chamberlain tied with most FTs in a game all-time, at 28/32, Adrian Dantley also had 28/29.
Interesting about Wilt, given that he was a lifetime .511 FT shooter (a .613 best, a .380 worst ... .380!). Dantley, on the other hand, had a career average of .818.