As suggested here on this site, I have a painter's canvas drop cloth to use as a couche.  It is 5'x15' - a bit large for my needs.  I'm wondering what would be the most practical size to cut.   I'm thinking 3'x5'?  3'x2.5'? 

Also, since it was not intended for food usage, should I wash it first?  I planned to, but don't know if it will get too soft. 

 I was able to find rice flour for dusting it at a middle eastern market.  It is very fine- like dusting powder or cornstarch.  Is that the right stuff?  I have always used cornmeal on parchment so I want to check before I start.

The dough I have rising is quite slack, so any thoughts on that would be great.  (I may just stick with my parchment for this loaf...)

 I appreciate any ideas.  Those are the questions I've thought of, but if someone has other tips I should know, please send them on.

Thanks,

Marni