Is their a simple method for shrinking 100% cotton t-shirts? They are
5X large and need to get them to 4.5X!  If hot water is the only way,
please let me know any tricks that are known. Any do's and don'ts.

Steam works too -- get it from a clothes iron, hot steam shower, or a
wet towel in the clothes dryer.

IF they are *not* poly/cotton blend and/or "preshrunk," then hot water
(or steam as mentioned above) is the only way.  However, if the tag
says any of the above, or "mercerized," then you're not going to be
able to shrink them, unfortunately.  If it's absolutely necessary to
have them smaller, they could possibly be cut down and resized.  It'd
be a pain in the neck, but is a possibility for someone with
experience sewing with knits, and possessed of a good serger
(specialized sewing machine).  Good luck.

Wash in hot water, and dry in hot drier.  Do this more than once if
necessary.  They will shrink. It works... especially on 100% cotton.

Regards,

tlspiegel

I have had some success in shrinking cotton items by ironing them with
a hot iron while they were VERY damp (almost soaking wet). Push the
iron from the outer edges of the garment toward the inside so that the
garment is not inadvertently stretched as you iron. Keep ironing until
the garment is dry, then throw it in a hot clothes dryer.

Note that this may cause uneven shrinkage, and the neck, sleeves, and
hem of your T-shirt may be a bit wavy as a result.