How do you properly sticky jump?
I've taken a sticky jumper for a test run from the store as I have to admit I'm not really good at sticky jumping. (It also makes a great combo with the pain train for back capping purposes.)
What I try to do is place a sticky on the ground, walk over, jump and ignite when I'm at the peak of my jump. Most of the times, that only gives me a lot of self damage and barely any propulsion. Other times, I can cover great distances.
I've tried using two stickies instead of one, but that ends either with a suicide through self damage or a suicide through that and fall damage.
What's the idea behind a textbook perfect sticky jump?
Solution 1:
Crouching while in the air lets you travel higher and further than normal.
Let yourself be overhealed by a medic before you sticky-jump to minimize the risk of not landing alive.
And lastly, as you also mentioned, the more stickies, the higher and further the jump. You will need to overheal to perform sticky jumps of three.
The technique is simple:
Walk to your sticky, jump over it, and when you are just about to reach peak height, detonate. You should be in front of the sticky to boost yourself forward when you detonate, so jump accordingly.
There is a training weapon called The Sticky Jumper with which you can train jumps, or even just use them in the game to fast travel.
It can either be crafted, traded or bought in the store.
Solution 2:
Sticky jumping requires practice. I'd suggest practicing on a map like ctf_convoy, where falling means you die and you can respawn and try again quickly. If you're good at sticky jumping, you should be able to cross between the two convoy trains from a variety of positions. 2fort is another good 'live' training map. From the front entrance, you should be able to sticky jump to the battlements with a single sticky. 2 stickies should take you across from one battlements to the other.
In addition to these maps, there are jump challenge maps (usually that start with jump_ so you can find them on the server browser more easily) where you'll be presented with a set of difficult jumps to attempt. It can be good practice, although it is sometimes frustrating.
What you want to do is, put one sticky down in front of you, and then run at it full speed, and jump + crouch, then detonate it. Depending on your timing, you'll either go up at a high rate of speed, or forward for a good distance. You'll have to practice so that you understand the correct timing for doing either move.
In general though, the later you detonate, the more forward momentum you'll get, and detonating sooner will result in more upward momentum. Using more stickes will take you further, but at a cost of more of your health. You'll have to balance the advantage of getting somewhere tactically useful with the disadvantage of having less ability to fight when you arrive.
This article on the TF2 Wiki is also a good source of information.