1. On latest Windows version I am on now it works as the classic paint. 2. On classic paint you set colors > rectangle > select filling (w/ outline or w/o). On new paint is set colors > rectangle > fill > select filling > outline > select outline. So 1 or 3 more if you want to remove the outline.

Number 2 took me from using paint constantly to just using photoshop instead.

1. Use shift+click.

I still find myself trying to do #1 frequently