The front flares are a bit more involved due to the support bracketing underneath. Take your cut flare and place it back on the vehicle noting where the support bracketing is underneath. You will need to cut the support brackets as well, so mark where the flare sits, and then cut back on the support approximately a half inch to an inch back from the edge of the flare. Note where the bolts are on the support as you do not want to cut this far back into it. Before you cut the support, move your side marker light wiring so you do not accidentally cut it. For this step I had a saws-all that I used. You can use the dremel if that is all you have, but it will take you awhile.
Now that you are satisfied with your flares, put them back on using your original hardware. I finalized the look by getting some black door edging from your local autoparts store. It fits perfectly and has not come loose. You will need two packs of this to fully cover all four seamlessly.
Once you are satisfied with your cut take a 1/4 sheet of 220 grit sand paper, and roll it to about the size of a cigar. take this roll and work it along the trimmed area, being careful not to get it up on the painted area of the flare. You should be working just the edge to get the final de-buring done.
The rear flares are pretty simple because you don't have any support underneath that you will need to cut. I recommend you do both of the front flares or the rear flares at the same time so you can make them symmetrical.
After you are done with your cuts, go back and drag a razor across the cut area to de-bur the flare to get all of the melted pieces off of the flare. The pieces will easily break off. at this point check your cuts by holding the piece up to the JEEP to check see if you cut enough or if you want to cut more.
After you make the initial scoring cut, go back and make your cut again, this time going through to the other side. You don't want it too deep as this too will make the turns more difficult. As you get to the turn area, watch the back side of the blade, as this can come in contact with the side of the flare that you want to remain intact. this can be unsightly so give yourself some room by opening up the cut on the side of the flare that will be discarded.
Once I was satisfied with the area that I wanted to cut, I took a high speed cutting wheel on my Dremel and started my cut following the blue painter's tape. Go with the natural cutting direction of the dremel which is from left to right. By doing it this way, your dremel will stay smooth with it's motions and not want to jump around on you. The plastic will begin to melt while you are doing this so you need to move fast. Sometimes it is easier to make a scoring cut first instead of all the way through so you have something to follow. It also makes it easier to turn the cutting blade when you get to the corners.
I didn't do a thread on it, but I would be glad to tell you what I did. First step is to remove the flares off of the vehicle. Some people leave them on, but my line of thinking was that I could get better angles by taking them off than leaving them on the vehicle. I took some blue painter's tape and taped off the area I wanted to trim. Remember that you can always take off more later, but you can't add it back so be sure to give yourself some wiggle room with your cuts. I decided that I did not want it to be perfectly flat so I left about an inch on the sides of the flares still intact to give it the appearance of being a bit thicker than the thin plastic that it really is.