Digital BW, The Print

I would like to hear from others who are using Lyson Print Shield (or equivalent) to spray 
RC papers. What techniques or tips are you using?  I can't for the life of me seem to be 
able to get the print neatly sprayed without mottling the deep black areas of the print - 
even with 5-6 light applications.  Not until I spray the print quite heavily until it is almost 
wet does this problem disappear but then that's right on the borderline of too much.  
Dealing with dust is a major problem but I guess that it another issue.  Any thoughts 
would be appreciated.

Regards

Steve