Cleaning a white Clark tank

[Veldbrand]

It seems that the white Clark tank I have picks up dirt on the sides where ones knees rub against it very eazy and trying to keep it clean is a mission.
Anybody use any specific product to clean theirs or avoid this?
I've picked up from other threads that adding stickers doesn't seem to work too well to prevent or disguise it either.

PS. And before you say it, yes I do have a decent washing machine...

Thanks in advance.

 

[theotherguy]

 

[Vulcan]

 

[Veldbrand]

 

[XTFREAK]

 

[lecap]

 

[XTFREAK]