Hi all, I want to run a coax into to my house bedroom because I'm disabled.
I recall reading having a short piece of electrical pipe placed through the
wall and sealed after the coax is run. Any other ideas? How much of a tail
should brought into the room?

What I did, for my ingress points, was to mount a standard square
metal "outlet box" on both the inside and outside of the wall. These
boxes have punch-out openings in the back which are of a good size to
accept a standard piece of male-threaded iron pipe (a "pipe nipple")
that's long enough to go through the wall. The pipe nipple isn't
large enough in diamater to allow a coax fitting to slide through it,
but is large enough to take the coax itself... this means that you're
likely to have to install the N or PL-259 connector after feeding the
coax through.

I actually fed four coaxes into the house, through a pair of pipe
nipples located in the diagonally-opposite positions in the box. I
then "punched out" four of the side positions in the box mounted on
the outside wall, and mounted female N connectors in the holes. Each
N connector is wired to a length of RG-8X, which is fed through one of
the pipe nipples, out through a punch-out in the bottom of the box on
the inside of the wall, and up to the back of the desk where my rigs
are located.

The outside box is connected to a ground rod, which is also hooked to
a heavy wire that bonds it to the main building ground system. I've
got some N-connector Polyphaser surge suppressors connected to the
female N connectors on the outside box, and the coaxes to the antennas
connect to these.

As to how long a tail you want: you can either bring in a tail that's
long enough to reach your operating position without tripping anybody,
or you can install a short tail and (e.g.) female connector, to which
you then connect a suitable jumper cable to your rig. You don't even
really need a coax tail - you could install a box or panel inside
which has several female connectors on it. This would probably be the
neatest sort of indoor installation, as you can detach all of the
coaxes from it if you wish in order to clean or to rearrange the room
or etc.

Other options are available. MFJ makes ingress panels, with
connectors and/or sliding gaskets for a coax to fit through. They
make them for in-window mounting, and for replacing a soffit vent in
an under-the-eaves mounting position.

If you have an under-the-floor crawl space, you could probably bring
the coaxes in under the building through a vent (make sure to seal
around the opening to keep critters out), drill up/down through the
floor in a convenient corner, and snake your coaxes up that way. Or,
cut out an opening and flush-mount a box with RF connectors in it.