Whiteboard Challenge Task 3

I really struggled with this task, as I found it hard to come up with a meaningful task incorporating the 'transparency' feature. Of course, I could just have used it to make a fancy background to my flipchart page, but I wanted to actually do something with it. I finally came up with the idea of using it when teaching time to my Third Years.
I created a flipchart page in ActivStudio 3 and inserted six blank clock faces, with a time written in Spanish underneath each one. Pupils came up to the board to draw the hands on the clock, according to what it said underneath. I then used the 'transparency' feature to make the text disappear, and pupils then individually wrote the times in Spanish into their classwork books, before coming together to feed back on the IWB.
I chose to make the text disappear, rather than the clock faces, as it is obviously harder to produce Spanish than to recognise it. Therefore, in this way we started with the easier task of text recognition before moving to production.
I was pleased with the task although the process to make the text transparent was somewhat laborious - possibly I have missed a shortcut? I would like it to be one of the options when I rightclick on the text.
I am interested to see what other language teachers have done with this task, given my lack of inspiration at the start.