Ten

Once a person has had their aura nodes opened, they must learn to keep their aura from leaking away from their body. Ten
(纏, Envelop; Shroud) is the process of keeping the nodes open, but also
having aura flow through and around the body rather than away from it.
Once maintained, it creates a shroud around the user that feels similar
to standing in lukewarm, viscous fluid. Having a shroud of aura surround
the body is the most basic defense against the emotional attacks from
other users of Nen, however, it can't defend against Nen physical
attacks.
Ten maintains youthful vigor and reduces one's aging; since the energy
powering the body no longer leaks away, one can keep the body from
breaking down and deter the aging process. Through frequent meditation, one can improve the quality of their Ten.

Zetsu

While Ten allows a user to keep aura from leaking away from their body, Zetsu (絕, Suppress; Null) stops the flow of aura from their body altogether^.
By closing all of their aura nodes, the user is able to stop almost all
outflow of their aura like water from a valve. Since the user is no
longer surrounded by their own aura, they are more sensitive to the aura
of others. This can be useful when tracking another person and it will
also prevent other users of Nen from noticing them. Zetsu can also be
used to relieve fatigue, since it forces the body's external layer of
aura to be fully contained within.
However, since Zetsu involves shutting off one's aura, it can be
dangerous due to it leaving the body defenseless against any aura
attack. Even a weak attack enhanced with Nen could do massive damage.

Ren

Ren (練, Refine; Enhance) is a direct application of Ten.
Since a user is capable of keeping aura from leaking away from the
body, it's also possible for them to produce more aura around themselves
without having to worry about losing it.
Ren focuses on outputting a high amount of aura and keeping it on the
body, expanding the size and intensity of it. If Ten is considered to be
purely defensive, then Ren typically what is used for offense. This
increases the user's physical strength and durability and provides a
large pool of aura for any advanced techniques or individual skills they
decide to use.

Hatsu

Hatsu (發, Release; Act) is the release or transmission of
one's aura so it can be projected to carry out a certain function. In
essence, Hatsu is one's personal expression of Nen that creates a
special and unique paranormal ability (colloquially called a Nen
Ability).
A good Hatsu should reflect a person's own character; one can never
truly master Nen if they only copy other people's abilities.

The 4 above are the basics of what we can do with all of our
energy.  If you want, you and I can create new names for them to make it
easier for us.

Gyo (凝, Focus) is an advanced application of Ren by which a
Nen-user concentrates a larger than normal portion of their aura into
one specific body part. Gyo increases the strength of that one body
part, but leaves the rest of the body more vulnerable. Gyo is
most often used in the eyes, allowing a Nen-user to see aura and things
which would otherwise be hidden (e.g. Nen objects hidden by In).

Shu (周, Enfold) is an advanced application of Ten. Shu
allows a user of Nen to extend their aura's envelopment onto an object,
allowing them to use that object as if it were an extension of their
own body. For example, one could use Shu to extend their Ten around an object, which would strengthen and protect the object like the way Ren
strengthens and protects their body. This is the technique that allows
Hisoka to make his solitaire cards as sharp and as hard as metal knives.

Ken (堅, Fortify) is the advanced version of the basic Ren technique. Ken is a defensive technique where a Nen-user maintains a state of Ren over their entire body, allowing them to defend against attacks from any direction without the need to use Gyo. Ken is as useful as a defensive position, but is tiring to maintain. Additionally, it is not as strong as Gyo
on any given part of the body, since it protects the whole body evenly.
Because of that, it is used to guard when one wants to be cautious.
These
are the three advanced techniques that you and I are going to focus on
for shielding. I'm not certain what is going to work for you, or if a
tool will make it easier for you to make it work for you so we'll
practice some things.