Modifiable progress bar symbol in Sketch

I'm trying to create modifiable progress bar symbols in Sketch. Those are rectangular and circle one on the picture below:

To modify that rectangle so it would suit different percentages I created separate progress bar symbols to nest in the main one like so:

I don't think this is the only way of modifying progress bar. A while ago I saw a tutorial how one guy regulated progress length bar using text override. He somehow linked mask to the text field. Thus, he could regulate the length of the progress bar with the amount of text symbols typed in the override. I can't find the example and forgot how he did that.

How can I create one progress bar symbol and modify progress bar without creating additional symbols for each percentage?