Remember that while it is citrus, it is still VERY CAUSTIC and powerful.
HIPS: Use different support slicing than you would normally with ABS supports. You need 0 offset for support, where typically when you print supports with the same material as the object you have a support offset of .1 to .3mm. 0 for HIPS.
Pull as much HIPS off the object as you can with pliers. No need to dissolve most of it, it will just pull off.
Keep two jars of DL available.
The first jar is your dirty jar. Put your object in there, let is sit, shake it, let it sit, etc. At some point, the HIPS will get soft.
Next object you do can just follow into the dirty jar. Its used to soften the HIPS.
Take the object out, and see if you can remove more of the support with needlenose pliers. Sometimes this is enough.
If not, put the object into the second jar of CLEAN DL. Let it sit, shake it, let it sit, etc, until your object is clean.
That being said, dont expect TOO MUCH. Its not that great an approach, and you may just go back to normal supports. The first problem is getting a good dual print, where the HIPS doesn’t dribble where you model wants to be ABS, thus creating holes in the object when the HIPS is dissolved.
But its a fun thing to try, so have fun and good luck.