The only removal method for a non-soak-off gel is to file it off.
To answer your next question, we know that most gels will adhere to acrylic with the right surface texture. I personally have done this many times. You file the gel as thinly as you can using a 150-grit file, being very careful not to break through to the nail beneath. The existing gel surface must be rough for the acrylic to adhere properly, if it is too smooth you take the chance of the acrylic popping or separating from the gel that is left.
If you have broken through to the natural nail while filing and thinning down the existing gel, stop immediately. The 150-grit is way too harsh for the natural nail and will damage your client’s nails. Make sure you do good prep work too. Improper prep is the biggest reason for lifting.
— Renee Doran is an educator for OPI.