according to the no daze mosaic adhesive people you are supposed to be able to grout as soon as it cools off. havent tried it yet tho

There is a method using mastic...by laurie mika? where you lay a bed of mastic and smoosh the pieces into it, therefore grouting it as you go-Im not sure how long the mastic takes to set up. Thinset I spose would work too, again I dont know how long it takes to set up.
Aside from that, silicone sets up quickly and even though you are supposed to wait, I have grouted within hours of using it. on a simple flat tile or something it should work. Do a test piece and give it a shot.

Exactly what WACKY said was gonna be my suggestion - push and sqush. We'd make a team, WACKY.

Then send em to us!lol! You get em hooked...we'll take over! Bwahahaha!

Thanks for the advise - I'll try a test project to see how soon I can grout. Yes, after I hook 'em with the beginner's project I'll send them to you guys to reel them in! LOL
Herself

Goodluck and please let us know what works best for ya

Herself...

Here is a link that might be useful: Conversation (Treasure Hunt) stepping/garden stones