Slap and strum technique question

Question

I am trying to learn Bella Ciao arranged by Rodrigo Yukio. How do you play when a part requires you play slap and strum at the same time? (See the image below) Do you use:

• only the index finger?
• middle+ring?
• index+middle+ring?

From the video it seems like Rodrigo is using the third alternative, but I might be wrong. (Video Time: 0:08)

There is also this part where I can see that he is using only his middle+ring finger only? (Video Time: 0:14):

I have seen some lessons on this topic where some people slap and strum with index and some other suggest ring+middle? Is there any situation where one is better than the other?

video link:

Answer 1

I use to strum with all fingers right before slapping: It's the same downbeat (just strumming the strings by stretching the fingers right before stopping with the flat hand - all 3 of your variants are possible).