I am currently studying William levitts guitar book, V: 1-3. I am enjoying it immensely and find it a very helpful tool in furthering my study of music.

The question that i have regarding this book is that there are specific references in this book that are regarded as picking exercises and others that do not specify whether so.
It does not say anywhere if i should be using a pick or if i should be finger picking.

In the first few lessons for instance there are a few "songs" that use the 4th string and 2nd string together in unison. Should i muting the 3rd string and strumming the 4th and 2nd or am i finger picking just the 4th and the 2nd

I'm not sure where in music notation it let's you know what to finger-pick and what to strum.

Thanks for your help!
I use "a modern method for guitar v1-3" too and i pick everything.
Somewher I read, that this book is made for playing with a pick.
if its saying in some places 'this exercise should be picked' then im gunna guess if it doesnt say u should finger pick it
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If it isn't finger picked, then it is played by a pick, and yes, it mostly looks like a riff (has some sort of evil tone, Trey Azagthoth of Morbid Angel used it a lot on Altars of Madness) but you mute the string in between with your index finger. It takes small amount of time to practice, couple of hours, I've had that problem when I started playing Immortal Rites by Morbid Angel, now it's no biggie to play it. So yes, muting the string is the way to go if you're playing with a pick