modeling chocolate would be the best medium to use; the recipe I use comes from Mike McCarey and is 2# of white chocolate chips and 1 cup of white corn syrup. It’s best to do this in a clean plastic bowl and use a non-stick spatula to stir.
Gently melt the white chocolate chips, if you scorch them, you can’t use them. When they are melted and smooth, heat the corn syrup and while still warm, add the corn syrup all at once to the melted chocolate and stir until combined (don’t over stir or over mix) Pour (scoop) the mixture out onto a sheet pan lined with plastic wrap and chill until set. Knead it for a minute or two, then wrap well in plastic wrap and store in a ziploc bag. Use powdered color or candy color to color it. You can also add color to the corn syrup but your whole batch will be that color….
I like to make it the day before I need it.
If it is oozing, it means there’s too much corn syrup in the chocolate or it’s overheated. Once the mass is overheated you can’t work with it any more.