How do you get from the Grand Street subway station to 9 East 91st Street in Manhattan?

This is the best route that I can find: take the Uptown Bor D (of the B-D-F-M, the orange line) from Grand Street (at Chrystie Street) to West 4th Street.

Transfer at West 4th Street to the Uptown E (of the A-C-E, the blue line), and take the E to 53rd Street-Lexington Avenue (which is the last stop in Manhattan on the Uptown E before it goes to Queens).

Free transfer is available between the 53rd Street-Lexington Avenue Station on the E train and the 51st Street Station on the 6 train, of the 4-5-6, the dark green line (as opposed to the light green line, which is the G train, the only subway line that does not run in Manhattan).

Take the Uptown 6 from 51st Street to either 86th Street or 96th Street (at Lexington Avenue), depending on whether you want to walk 5 blocks uptown or 5 blocks downtown.

The address 9 East 91st Street is between 5th and Madison Avenues. Madison Avenue is 2 avenue blocks west of Lexington. Park Avenue is between them.