Couple of days ago we had a few dry days so I did it. Actuall, I did our Miata as well as the 135i. I Washed the top off with soap and water using a soft brush, then hosed it off really well and let it dry for a day.
Next day, I used thin plastic painters tarps, the really cheap thin ones to mask off the windows and paint. I put the soft top part way up and draped sheets of plastic over the front windshield, the side windows and the back end and then closed the top on the whole thing so all I really had to deal with for overspray was the back glass window. I sprayed 303 on the fabric until it was saturated and then let it bake out in the sun all day. Came out really well, tended to darken the look of the fabric and even out the splotches and water beads up on it now.
I keep the car in a semi protected carport, but when I happened to look up the cost of a new top the other day I was shell shocked...
$2500 and that's just for the top, without installation.
I'm definitely going to recoat this about once a year or as needed to get as many years out of it as I can. Anyone know a better price?