What free promotion websites are there?

Question and answer, self-media, soft text, post bar, forum, classification, etc. These are all things, but they are not really free, and both labor and time cost. We often do promotion, find someone to do 100 degree search promotion, or bid, or use questions and answers and soft articles, and the drainage effect is very good. If you are interested, you can find and push it online. It is not expensive, and it is a skill.