Have things changed and now that Brightline apparently runs from downtown Miami, is there a convenient transit link between the Brightline station in downtown Miami and the Miami airport?

I've searched online and it looks as though Tri-Rail serves both the airport and downtown Miami, and Brightline runs from downtown Miami, but I'm not clear on how easy this is in real life, particularly on a weekend. I have a connection between MIA and Brightline tomorrow and would appreciate any insights as to how to make the trip between MIA and Brightline, and how easy it is in real life to use transit.

Thanks.