I recently watched a show on tv about sweepstakes, they featured a man who enters 400 + sweeps a day. My question is: how do you find that many to enter a day?

  Welcome to SA Blue77! You will soon find that it isn't difficult at all to enter 400 sweeps a day.

Many sponsors have multiple sweeps going at the same time, and can be entered quickly while you are logged into their sites (Hearst Publications, ie Country Living, House Beautiful et al, are great examples).  Watch for different creative presentations of the same contest also (the larger the prize, the more options there are).  HGTV and Frontdoor are good about letting you know for example, and will show you links to those contests as you enter.  There are several "one per day/contest" sweeps that actually have 2 or more (many more) entry options.  It adds up fast and can increase your odds.

There are many more sweeps than those listed here, especially Facebook.. watch the pages as you enter for links to other opportunities, and share when you find them!  Try this link, it pops up sometimes when entering FB sweeps.

https://apps.facebook.com/sweepstakeshq/contests?contest_format=sweepstakes