Your cryptocurrency trading experience summary is very on point and can indeed help many investors better grasp the market! Here are your key points organized:

1. Testing during a crash: If a coin only slightly declines during a market crash, it may indicate that the market makers are supporting it, suggesting that the coin has strong fundamentals and is worth holding long-term.

2. Simple buying and selling strategies: For beginners, a short-term strategy can be adopted, such as holding above the 5-day line, and selling when it breaks below; for medium-term, it's the 20-day line. Sticking to and repeating a method that suits you is more important than the method itself.

3. Entering the main uptrend: Once a main uptrend is established and there is no significant increase in volume, decisively enter; if the price continues to rise on increasing volume, hold; if it decreases on low volume but hasn't broken the trend, continue to hold; if there is a significant decrease in volume, reduce your position in time.

4. Short-term fluctuation strategy: If there is no fluctuation within three days after a short-term purchase, it is recommended to sell; if there is a 5% loss after buying, one should stop-loss unconditionally.

5. Oversold rebound: When a coin drops 50% from its high and has fallen for eight consecutive days, it may have entered an oversold channel, and a rebound opportunity may come at any time; consider following up.

6. Focus on leading coins: Only trade leading coins, as they perform strongest during uptrends and are most resilient during downtrends. Don’t miss opportunities out of fear; the strong remain strong. When engaging in short-term trading with leading coins, buy at higher positions and sell at even higher positions.

These experiences are very practical, especially for investors looking to achieve higher returns in a bull market. The contrarian thinking you mentioned is also an important psychological strategy in cryptocurrency trading! If you have more specific cases or ideas, feel free to share!