I actually use a staking set to install hands.
For the hour and minute hands I use a hollow flat stake, choosing a hole size that just fits over the minute hand arbor for the hour hand, and one that just fits over the seconds hand arbor for the minute hand, and pushing down gently by hand (no hammers). That way the stake comes up against a positive stop when the hand is in place and the tendency to push the hand too far down the post is eliminated. As a result there is almost always sufficient clearance between the hour hand and the dial, and between the hour and minute hands, the hands always go on square, and the only time any adjustment is necessary is if a hand is bent out of its correct shape.
For the seconds hand my staking set has a stake with a plain, flat, brass tip and a plastic ball on the top (so designed for pushing by hand rather than hitting with a hammer).
As far as supporting the other end of the seconds hand arbor, this has never been an issue for me. As a rule, if you have to apply a lot of force to get the hand on to the post then its probably the wrong size hand. It should really only require light pressure to get it to seat, but nowhere near enough to damage the supporting bridge or jewel. If the movement has an indirect driven centre seconds hand with a tension spring bearing on the end of the arbor then this should flex enough to allow the shoulder of the arbor to contact the jewel or bridge for support without any harm coming to the spring.
The exception to this is chronograph centre seconds hands. When you reset the chrono the seconds hand rotates back to zero very fast and comes to a sudden stop. Because of the length of the hand and the speed of rotation, inertia is likely to cause the hand to slip around the post when the post stops at zero so unless the hand is a tight fit, it would be constantly going out of alignment.
For this reason you should always use the correct movement holder which will have the proper support for the lower bearing built in to it.
Basically, use the right movement holder for chronos, and a light touch for everything else.