How to master "Watchlist Specialization" for swing trading while running a full-time business?

I’m looking to start swing trading, but I have a major constraint: I run a business full-time and cannot spend my day staring at 1-minute or 15-minute charts.

I’m interested in a "Watchlist Specialization" approach. Instead of scanning hundreds of tickers, I want to build a deep understanding of just 5–10 specific stocks—learning their cycles, how they react to news, and their typical "floor" and "ceiling" prices—so I can buy when they are undervalued and sell on the recovery.

**A few specific questions for the community:**

* **Selection Criteria:** How do you choose your "forever 10" stocks? Do you stick to high-volume blue chips, or specific sectors you already understand through your career?
* **Resources:** Are there any known traders, books, or systems that specifically teach this "narrow and deep" approach rather than broad market scanning?
* **The Reality Check:** Is this a viable long-term strategy for a busy professional, or am I setting myself up for "concentration risk" by not diversifying my watchlist?

I’d appreciate any advice, resources, or even warnings if you think this approach is a trap for beginners.