To establish baselines or bases, you need to easily spot clear cracks/dips. High volume of buyers and sellers is also something Luc repeats in his videos. Therefore, larger, more established exchanges are best for this trading method generally speaking, especially for newbies.
Luc shows in at least one video that he traded on Liqui, a cool exchange, but smaller than Bittrex or Binance or Kraken. He showed a situation where that exchange had a larger drop than larger exchanges. Big trades, but he ultimately decided to move his cryptos out of liqui. Even someone experienced like Luc will need to move coins off an exchange if fearing issues on the exchange will inhibit entering or exiting trades. You typically see issues on smaller, less established trading exchanges.
Your last question is one I've been asked and one I would think is a concern to many people. I've wondered about this too. Luc mentions on a few videos that he plays obvious, steep, voluminous cracks. He does "nibble" on smaller ones, but he remindes newbies to play it safe. The best way for us to play safe is to look for those steep, big cracks. Set buy-in to make money and keep your risk as low as possible, so set your first purchase target for 25% below the most recently established base and two more buy targets at 10% lower each in case the crack becomes huge . To get good at seeing these, you'll need to look at the month, or even three months. You might not be trading as often only playing the big cracks, but they're safer to start with. Once good at that, then play more often, use different currency pairs, try smaller cracks. It's less about "distance" between cracks and more about severity of cracks and volume. Find where those happened historically to spot if the setup you're looking at in the present seems to match up for a predictable dip and bounce.
Anyone else want to comment on the question or my response?