I haven't had masking tape residue, but the other day I put fusible interfacing on some fabric with the sticky side up. Fortunately I always use a pressing cloth so no harm to iron. I was able to get it off with very little effort by saturating the fusible interfacing with water and it lifted off fairly easily. I used ice on the residue which made it coagulate a little and I got off all the residue.
I use ice or ice water a lot for stain removal. The ice makes it glob a little and then you can get it off in chunks instead of spreading it around.
Good luck. I hope this helps.