step 1: OMG I hate silicone. I had one tube of black, and it worked great (except for the fact that silicone is super difficult to spread apparently.) No stinky smell, noxious fumes, nothing. I ran out quickly and went to buy 2 more. (only used 1..) But I bought a different brand. (still 100% silicone) This brand was the worst idea I ever had. Smelled horribly and made me light headed instantly. I was doing this in a well ventilated area but it was no good. I worked as fast as possible and booked.
step 2: Next I siliconed some corkbark and driftwood into place, and started with the great stuff. wow, was this fun..
step 3:

yaaaaaay, done being foamy. I added a feeding mushroom ledge and carved a cave out of a blob I made on purpose.
and that is all for now. I was going to sand off the shiney-ness of the GS (someone on another forum suggested this would help the silicone to adhere better) and also sand around and inside the "cave."
tomorrow is coco-fiber time!
Any suggestions, questions or comments?
-Andrea