I have never used it before but if it takes 15-20 minutes before sanding it would never be useful in a production body shop. A good body man can have a "1 hour" dent worked out, filled, sanded, feathered & in primer in 20 minutes. I can't tell you if its any good because I don't know anything about it, but I would use a good light weight plastic filler. Maybe someone here who knows what it is you have can tell you more about it than I can.

1957 Chevrolet 1/2-ton Stepside LB in the Gallery
My Photobucket shots

The person who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself." - John Stuart Mill (1806 - 1873)