When I need to quickly switch between two blocks of code, I add in this construct to speed up switching:
//*
block1
/*/
block2
// */
which comments out block 2 and leaves block 1 uncommented. Then, I just have to delete the slash at the start to simultaneously uncomment block 2, and comment block 1. However, if I comment out block 2, the IDE highlights both blocks as though they're not commented.