Digital BW, The Print

Hello

I am interesed in possibly using the PremierArt Print Shield Spray.  
I use Photorag and William Turner paper with the MIS UT2 inks.  Is 
the PremierArt Print Shield spray used with the Photorag and William 
Turner Inks?  When do you apply the spray to the paper - before or 
after printing?  Does the spray provide a higher DMAX or is the spray 
only used for greater archivability?

Thanks for all responses in advance.

Regards
Ross