I am getting ready to apply for Aid and Attendance pension for father who is veteran. What is the best and fastest way to apply for VA benefits?

I applied for my mother through the local Veterans Service Agency through our county government. It didn't take long and it was free. The service officer even pre-filled out the paperwork and looked up my step-father's service record, etc. It was easy for us! And she handles any changes for me also.

By getting an Advocate to help you. You can google VA Advocate and find one reasonably close to where you live. They will help you with the paperwork and tell you what you can and should apply for.

You can get expedited filing if your LO is over age 90. Otherwise, the best advice is to ensure that information submitted is accurate and complete. Most of the problem comes when applications are bounced back for additional information. When resubmitted, they go to the back of the line. If you're good at detailed paperwork, go for it. Otherwise, find someone that knows what they are doing. BTW, when approved, they will send the arrears payments based on the original application date.

I did a claim for my FIL last year, through a VA Specialized Attorneys office who does nothing but A&A claims for a fee of 700 dollars, and the claim was completed in about 5 weeks. We turned in what was called a FDC, a FULLY DEVELOPED CLAIM, which supposedly Fast Tracts the claim through in under 3 months, and it worked for us, plus he was paid back to the day we applied. They also take care of any questions that come up on his claim for life, no additional fees ever.

My FIL only lived 4 months while collecting the full A&A ($1,774 per month) benefits, but he was tickled that he even got Something for his services in the Navy all those years ago! The Navy also provided him his ingraved headstone an American Flag for his coffin, and would have provided a 21 gun salute, but we didn't have a traditional funeral, so didn't utilize those services.

Its a lot of work, gathering their appropriate ppwk, but So worth it in the end.
I would definitely recommend you investigate the FDC through the VETERANS BENEFITS ADMINISTRATION, as it does fast tract the claim for you, but you must make sure that every line is filled out. 

Good luck with your claim. I was allowed to use my POA on most forms, but my FIL did have to personally sign several forms, and we did have to attach all of his Navy ppwk, as well as a blank checking slip, for his benefit monies to be deposited into. The VBA will tell you exactly what forms need to be sent. I know you can do this all yourself, but we did use the attorneys office for sake of ease, as well as their expertise. I hope this helped!

I applied on behalf of my mother back in May of 2017, the only thing I get each month is a form letter that they are reviewing our case. I call one time a month and ask. Her claim should be expedited as she is over 90.

I started with the County VA rep. Then if ur turned down you can get a lawyer.