Even after reading your question several times, I am not sure I understand.

I do not have any problems in creating tremolos.

Take a look at the attached image (done with Finale), showing two different types of tremolo:

Alternation between two pitches, and tone repetitions.

Which type are you trying to create?

Also, could you explain your difficulties with creating tremolos based on tuplets?

What are your steps? What does not happen that you expected? What happens that you did not expect?

The better we understand, the better we can help you.

The first type. I am not sure how to begin this process--the Easy Tremolos tool under Plug-Ins/TG Tools starts with, in my case, 4 quarter notes which Easy Tremolos turns into tremolos: eighth note, sixteenth note or thirty-second note or faster, but no indication to add the tuplet number (or addition dot). 

Do you use something other than the Easy Tremolos tool to make this? Your example looks great, and I would love it if you let me know how it is done.

Thanks!

I used a tuplet defined as “12 Sixteenths in the space of 8 Sixteehths”.

Following the “normal” procedure for using the plug-in Easy Tremolos I entered the tuplet as two notes of the same rhythmical value.

In this particular case (= 12-tuplet) the “two notes of equal rhythmical value” must be two dotted quarters (in order to fill a 12-tuplet).

This 12-tuplet occupies the first half of the measure.

In the second half of the measure I entered yet another 12-tuplet, appearing as two dotted quarters.

With these two 12-tuplets entered I ran the Easy Tremolos plug-in (setting the Total Number of Beams to 2).

That is all there is to it.

No problem really.

All right. I will give it a go.

My one concern prior to this is using 4 dotted quarters in a 4/4 measure, but looking at your solution, that shouldn't be a problem since assigning tuplets before entering the notes will take care of the "too many beats in the measure" problem.

Thanks for your help!