The best medium for brightening

[Xander Calceta]

I am encountering problems with my paintings when it is dry; it turned dull and pale. Is it because of the medium I use? I only use linseed oil by applying it on the canvas first before proceeding to painting and not applying on the paint itself for thinning.
Is there anyone of you who could recommend me a nice medium that would make my painting brighter or glowing? something that would prevent earth colors to sink or to dull out?
Don't recommend me varnishes because I have tried it and it just made my painting glossy but not bright.
I want to know the secret in brigther painting.

Please, anyone who has an idea about this share it with me and I know most of us here in this forum are interested with this.


thanks,
Xander