Filler primer! I just found out about this stuff and its amazing! 4 thick coats and like 90% of your layer lines are gone, it cuts down sanding time by a ton.
Ultimate Guide to Painting 3D Prints | MakerBot 3D Printers
The best filler primer for 3D printing? Filler primer test part 2 final results! - YouTube
How To Paint Your 3D Printed Parts | MakeitQuick
What Is The Best Primer For 3d Prints? – 3dprintscape.com