In the image below, the yellow Vindicator on the left is the first mech I painted out of the 'BattleTech Introductory Box'. The Cyclops on the right is the 24th and final one. I painted the yellow mech without thinning the paint at all and uh, it shows. I plan to strip down and repaint it, but I had to snap a picture for the archive.
What a difference practice makes. I saved this image to help myself remember that practice does actually help; it's just hard to notice improvement while it's happening. Hopefully after 24 more minis I'll be even better. Even with the difference in results, I had as much fun painting the first one as I did the 24th. That's what I love about this hobby: you can always improve but it's still fun and satisfying no matter what your skill level.