Preparation of a Solnhofen coprolite

[Yohoia]

Goodmorning, last month I went to Solnhofen for my last fossil trip of the year in Germany. I found a lot of fossils (ammonites, coprolites, fish, worms...) and now I'm preparing the specimens. I have basic tools, a Dremel 290, needles, awls. I prepare all of these fossils with succes, but a big coprolite is still covered buy a tiny layer of matrix, that I can't remove with my actual tools. It's possible to effectively remove the matrix left with acid? Tomorrow I will post a photo of the fossil. Thanks.