I have Lidocaine 10% spray in my SN protocol, but I will probably use a straw as well.
I tried the Lidocaine (2-3 sprays on my tongue): It didn't tasted good, but it really numbed my tongue for a few minutes.
As a test, I put some regular salt on my tongue and couldn't taste anything.
However, I can't say whether it really works for SN. That's why I'm going to use a straw as well.