Well..... iit depends on what your making as to how you use the PolyD.
First off--PolyD is not a substitute for sweetener. Even the PolyD Plus. PolyD acts as a texturizer for baked things and is used for texture in things like candy for it's crystalization effect (help me out here--Scott/Kevin/Island
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Second--if you are baking with it. You will get your best results if you mix the PolyD with the other dry ingredients well and then add the liquid.
Third--if you are using it in a wet application, you will get best results if you heat it with the wet ingredients and it it gets melted. Otherwise you get a chunk/glob of glue
Fourth--there is some reaction with Splenda and chocolate. Splenda + chocolate = bitter and nasty. You will have much better luck if you learn how to mix sweeteners--splenda/sweetfree, sweetone/ace-K, erythritol, xylitol, etc
it takes some experimenting with which one and how much.
Fifth--there are many threads on this board regarding the application of PolyD and sugar substitutes--usually found in the kitchen topic.
I am by no means the PolyD and sweetener expert--I'll leave that to Islandgirl, Scott123 and Kevinpa. They will be around sooner or later and they can give you more precise intructions.
Good luck!! Keep Cooking!!
Lisa