I'm an X-sewing machine tech. The easiest way to self clean your machines at home is the following:
Take a piece of cardboard light weight (not card stock) cut a circle and mark an X in the middle. Be sure the circle is larger than the vacuum hose. Tape straw to circle. Leave one piece of straw storter on one side. Make sure the circle is larger than the vacuum hose by about 1/2 an inch.
When you vacuum - remove the throat plate from your machine - stick one end of the cardboard w/straw in the vacuum hose. The vacuum will hold the circle in place. Now stick the other straw end inside the throat plate and move it around to get the lint out. This will remove the lint and many times will help stop empacted lint from forming.
If you can find some oil called "Tri Flow" get it. This oil is for small working parts (not plastic) that get used a lot, like sewing machines. It is not and will not get gummy and is the only oil most machine repair people use. It comes with a little plastic hose to insert in the top when cap is removed. Shake well before you use it and oil every thing that is a metal parts that moves, oil it. Most sewing machine repair people will not tell you about this product, it's a well kept secret.
For the lady that was threading her needle with presser foot down - The reason you thread a needle up is to not reset your tension disk. When you thread your needle down, you pull the thread and that throws the tension disk out of alignment.
I hope this helps.
Phaedra