I'm not sure how to close this, but the suggested thread had the answer I was looking for!
This was my end code if anyone is interested:
[btnRange addObject:@"12"];
[btnRange addObject:@"13"];
[btnRange addObject:@"14"];
[btnRange addObject:@"17"];
[btnRange addObject:@"18"];
[btnRange addObject:@"19"];
//start ordering
for (NSInteger i=0; i <= 5; i++) {
id nxt = btnRange[arc4random_uniform([btnRange count])];
btnOrder[i] = nxt;
[btnRange removeObject:nxt];
}