Sherwin Dubren wrote:

I have done a little research and see that seedlings can work (true to
type) but take a long time to fruit and may be not be hardy without
grafting them to rootstock.

Seedlings carry the characteristics of the previous generation, and
may
not produce the same fruit you are expecting. If that seedling came
from
a blossom that was pollinated from another tree, the probability of a
mismatch
goes up.

Citrus are about as bad about cross pollination as apples are.
It is very unlikely that you will get the same fruit quality from
a seedling, unless there are no other citrus trees of any variety
in your usrroundings - which in S. FL I find unlikely.

Any other methods I should consider?

A bud graft is where you attach the bud to an existing branch of a
tree. Other grafts
would involve attaching a piece of scion (a branch of your older tree)
to a root stock.
If you don't have another grapefruit tree to attach the buds, you will
have to get some
grapefruit rootstock graft some scion onto it.

Any citrus will do. Around here grafting is mostly done onto lemon
rottstock.

Maren, in HI.