I never felt the technique was different than playing a regular guitar.
Strike the strings with the fingers generally perpendicular to the plane of the strings, although I never worried about striking them 90-degrees to the string. My steel finger picks were always unevenly worn on one side.
If the fingers are too flat to the string or the fingers are too straight, it will be difficult to get the power needed to create volume. Most of the motion with the fingers comes from the knuckles on the hand, not the joints in the fingers. The finger doesn't bend much during the stroke. The muscles in the hand are stronger and the tone is stronger by moving the fingers from the knuckle joint and pulling thru the strings. If you are pulling mostly with the finger joints the tone will be weaker and snappy and may not sound the paired strings as well. The idea is too pull thru both strings.
Keep the wrist parallel with the arm. If the wrist is bent (arched relative the the arm), one risks carpal tunnel as the tendons move around the bent wrist while playing.
Finally, while these techniques will help one play better, there are many who don't rigidly follow them. For example, Tommy Emmanuel tends to bend his first finger a lot and he seems to do pretty well.
While I'm at it I'll plug one of my favs from the 60's, Dick Rosmini an uncredited player on at least one of the live KT albums.