The Right Hand
Position
These are images of the RH from the Progressive Classical Guitar Method by Australian guitarist Jason Waldron, a 3rd generation product of the London Spanish Guitar Centre founded in the 50's by Len Williams.
The a finger is placed perpendicularly and the thumb at 45 degrees creating the triangle with the a finger shown in the 1st image.
The i & m fingers are then placed with a slight slope inwards.
From the front. Note the position of the thumb particularly.
A Jolly Circular RH Thumb for okdaysdays
Showing the circular movement of the RH thumb and separation from fingers
Rest Stroke
I initially get my students to learn to execute rest strokes from the same position of the hand as a free stroke.
The Free Stroke position
I help my students achieve this by teaching them to use a prodding action by slightly collapsing the finger tip joint rather than a dragging action that most players start with that causes issues.
The Rest Stroke position
That prodding action is in effect a push in towards the sound hole from a hand carried directly above the string being played.
Beginners will often produce a double sound in their rest strokes because they pull the RH back up towards themselves when they wish to play a rest stroke. This action presents more flesh to the nail and hence it hits the flesh first and then the nail.
Learning to play a rest stroke using the same hand position as is used for the free stroke will normally remedy this annoying issue. Once a student has established a reliable rest stroke in this way, they are then ready to experiment with hand position in the interest of more facility
A Jolly Fingernail Shaping for gytaryst
My method for shaping the nails!
Pizzicato
Pizzicato is a wonderfully effective technique using the flesh of the side of the thumb.
You also need to make sure that you change the position of your right arm to accommodate getting the heel of the RH along the length of the bridge allowing you to pluck any string without having to adjust your RH significantly.
Here is a demo using the famous pizzicato section from Albeniz' Asturias