You're right! You dont' have to be pretty since you'll be covering the holes over with your vinyl soffit after cutting. If you're brave enough, and can set your tool to the proper depth, and can get it to stand up in the attic OVER the eaves, you can do your work from the attic! You just have to be careful you DON'T set the tool to the wrong depth and end up cutting a hole in the vinyl soffit!
If you set your hole to just under the wooden soffit's thicknes, you may be able to gently 'tap' the plug you cut to loosen if so you can pull it out (when doing this from the attic.) Another trick is to pre-drill a small hole in the center of the plug you're gonna cut, then cut the plug, then screw a screw INTO the pre-drilled hole and pull out the plug.
Have fun! And if you try the attic approach, make sure you have someone look outside while you do the first one to be sure you AREN'T cutting out the vinyl too!!! You can do a trial run or 2 at the back of the house if it needs to be done too. My best to ya and hope this helps.