Right/Best Ratio of Meringue Powder in Royal Icing?

Here's one response already from Kelly:

I use 6 Tbsps of meringue powder (CK brand) for 2 lb of powdered sugar.  I don't sift the sugar, but I do dissolve the meringue powder in water first (2/3 cup for 2 lb sugar).  I whisk it in the measuring cup, let it sit for at least a half an hour, then strain it before adding it to powdered sugar along with flavoring and 1 tbsp corn syrup.

I've used several brands and have not noticed any significant difference in the drying time or taste - 6 tbls to 2 lbs. icing sugar.  I add the dry powder straight in with the sugar, add water and proceed. Never have a problem with this method.

He leído sus comentarios, me ha servido de mucho...muchas gracias!!!..

I too add it (Wilton MP) right in with the powdered sugar and have had good results.