Check the old posts on this site. There was a thread on Toplac.
As I recall a very dissatisfied customer who did a DIY project with Toplac had bad results. Then an Interlux representative responded.
Toplac is reputed to have excellent flow characteristics and gloss and to be easy to apply for the DIY person. It is not as hard as Interthane Plus. Not sure how it compares to Brightsides.