I use this too - it does lack a bite like Wap says... one way around this is to give the mini a layer of dullcote to add some tooth (I actually use another Gunze product called Mr Super Clear which is pretty much the same as Dullcote)
But yes, it\'s smooth as you like. Grey is smoother, there\'s also white surfacer. Similar in smoothness are Tamiya\'s priming line, their grey is sweet as is their white (Tamiya Super Fine).
There\'s also Mr Base White 1000. Gunze do a whole bunch of cool products. I get the most use out of their liquid putty - it\'s basically watered down milliput and it\'s really handy for filling in pits in metal figures and sands down.
Other good stuff from there, Mr Mark Setter and Mr Mark Softer. These are excellent for decals.