The same lighter fluid (Ronsonol, etc.) that you use to clean shutters should do a fine job. What you might be finding, however, is that there's a plastic film intermingled; some hook-loop stick-on material uses double sided tape instead of glue applied directly, and in that case you have to get the solvent under the plastic before it can dissolve the adhesive (the stuff wiping off after sitting overnight is what I'd expect in this situation -- seepage takes time). I'd suggest gentle scraping with a plastic edge (old credit cards are excellent for this) to remove the bulk of the goo before another wipe down with plain lighter fluid or naphtha.