The most important aspect of this operation is to have the correct insert -- which is the course outer thread 1/4-20 style. Available at Lowe's The fine threaded inserts sold at most wood worker supply center are way too large on the outside diameter. It can be done but the course thread insert sure makes life easier.
Our fixture serves several purposes -- the tenon is gauged for size, it is securely captured to prevent split out, and the table keeps the installation tool perpendicular -- this is important, an insert that is out of alignment can cause problems down the road.
Here's the gadget we use to install the inserts -- purchased from Harbor Freight
The "insertion tool" is simply a cut-off bolt and two nuts, catch the insert on a few threads run down snug, hold the nuts with an open end wrench and reverse the drill motor. Oh -- the end that looks like a screw driver slot is really part of the tread cutting process and it goes into the pilot hole.
We apply a good bit of CA to capture the insert as well toughening up the end grain of the tenon.
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