I mentioned this a long time ago but it seems some were either confused or didn't feel like reading this whole thread! I don't blame you!
We always make a cereal mash for two reasons. One is you do need to boil the rice. We take generic white rice and put it in a blender and "chop" it into pieces that are basically round. Just put 2 to 3 inches of rice in at a time. If you put too much you get a lot of dust which becomes glue!
Two is we add some malt to the rice to keep it from turning into a big pile of glue! We do a mash with the rice and malt to convert the malt first and then bring it to a boil. This gives you some melanoidins from the malt which is a product of decoction which is always a good thing. We use half as much malt as rice and that's more than what's needed but we like decoctions.
Is all this extra work worth it? I believe so but that's always subjective.
Minute rice? Why not, should work fine just save some boiling time. Generic rice is also very cheap.
As far as corn is concerned, it does add some sweetness that is different from the sweetness you get from malt and the lack of hops. When Bud was 11 IBU's and above I liked it a lot but at 9 IBU's it's too sweet. However Busch is also sweet but I prefer that corn sweetness.
Brewmaster's don't call Busch a beer, they call it a mixed drink since any mistakes in pricier beers is blended off into Busch. It's at a level that would be really hard to detect though! Oh, and before anybody gets up in arms about that, it's totally legal to do. Now if they tried putting Busch in Bud, well then call the lawyers!
Man, I'm really rambling here and I'm not even drinking! Must be the cold medicine! Carry on!