Directly is a tricky word. In some sense you aren't doing things directly when you follow a step by step process.

If you however want a step by step process I can give it to you (but please don't complain that it's not direct enough):

1) You decide which emotion you want to feel.

2) You search in your mind for an experience when you felt the emotion in the past.

3) You visualize the experience.

4) In case that you see yourself inside your mental image, see the image as if you are seeing it through your own eyes.

5) If the image is black and white, make it colored.

6) Make the image bigger.

7) Locate the emotion inside your body.

8) Increase the size of the emotion.

9) Get it moving.

10) Give it a color.

11) Increase movement and size as long as you want.

That's the way of doing it I learned at day two of an NLP seminar.

I'm not actually sure of what you mean by 'directly' here. Which of the following does 'setting up the preconditions' include:

a) changing breathing patterns etc b) focusing thought on particular events etc. c) rationalising consciously about your emotional state d) thinking something like 'calm down, DavidAgain calm down calm down'

I doubt many people can simply turn a powerful emotion on or off, although I wouldn't rule it out. I read (can't find link now...) about a game where the interface was based on stuff like level of 'arousal' (in the general sense of excitement), which you had to fine tune to get a ball to levitate to a certain level or whatever. I'd be surprised if someone played that a lot with high motivation and didn't start to be able to jump directly to the desired emotional state without intermediary positions. And being able to do so obviously has major advantages in some more common situations (e.g. being genuinely remorseful or angry when those responses will get the best response from someone else and they're good at reading faked emotion, or controlling panic when the panic-response will get you killed)