How do I shop lenders?

[Anthony Viscuso]

I recently watched a YouTube video where a guy was able to shop rates for one of his refis by taking a letter of approval from one bank to another and forcing them to compete with each other's offers. He was able to finalize his deal with a loan rate of 3.75% on a 30 year fixed. I'm curious if rate-shopping is also possible with lenders for home purchases.

1) Can I get the lenders to compete without my having to fill out a loan application for each lender? (trying to save time)

2) If I need to fill out loan applications for each lender, will this affect my credit score negatively? (my wife and I are both above 800)

3) Is there any way to find out if I am getting the best interest rate since I'm not a broker myself?

Thanks in advance for anyone who replies.