What is the most efficient way to get your instrument rating?
The fastest path to any rating is intensive training.
If you can take time off from work and do an "accelerated instrument training" program you can probably knock out the rating in less than a month. That AOPA article says 8 days, I've seen a lot of two-week courses advertised.

Note however that there's a difference between being instrument rated and proficient for real-world IFR operations in actual IMC. These courses will almost certainly cram all the knowledge and procedures into your head that are required to get you to pass your instrument checkride, but you may have never flown an approach in actual IMC (if suitable weather doesn't pop up for you to fly in your time will all be simulated under the hood), and because everything is compressed and focused on "passing the test" you may come out of the program lacking the confidence to actually go out and use your newfound rating without doing some additional work with a local CFI (this is a point sometimes raised by pilots who have gone through these accelerated training programs).