renilla luciferase assay w/o quenching

[Helge Steen]

Hi all,

I am currently setting up a dual reporter gene assay with a renilla
luciferase and a firefly luciferase reporter in mammalian cells. 
I understand that there are kits available for the detection of both
luciferases in one test tube, f.e. Stop and Glo (Promega), that quench
the signal from firefly luciferase before detecting the renilla signal.
Now I would prefer to quantify both luciferases in seperate assays, in
order to get rid of the quenching reagent. My questions are:

- is it possible to measure renilla luciferase without quenching the
firefly enzyme luminescence?

- is a specific substrate for renilla luciferase available separately?

Thank you very much!!!

Helge