French Manicure Pens

I found French Manicure Pens by Rival de Loop Young in a local store of Rossmann.
They are available in five colours: white, rose, blue, green and black.
This is a try to make some stripes with the pens. But it turned out not that well...

First of all the liquid is too thick to soak the pen point from inside. Other way from the outside it hardened a way too fast. And the ingredients of the liquid were not very clear. First I thought it would be polish. But it doesn't solve in acetone. Maybe it was kind of acrylic paint.
Or maybe I am just not that skillful with the stuff like nail art pens...