I'm gonna try the 3M one here in a few weeks
I thought these pictures and comments may be of some assistance to you,
1, pic shows light cloudy oxidization, please note the bulk of the oxidization or cloudiness appears to be on the upper orange blinker area, but actually is right across the upper horizontal areas of the light,
Please also note, this headlight is the drivers side,
2,pic is same headlight at a slightly different angle, and I moved the light source slightly to provide another viewing angle of light reflection,
3,pic shows your passenger side head light, some clouding can be seen, but it is only the passenger side, so I would suggest your driver side headlight should or could have more oxidization,
4, shows same headlight pics 1 and 2 after 2 x 3mins quick buffs with G3 regular buffing compound, and big, ?? or normal size variable speed buffing machine,
5, Shows same ( 3, ) headlight at different angle, and I moved the light source slightly to provide a another viewing angle of light reflection.
6, shows passenger side headlight after 2 x 3min buff, the car owner reported the next day that lighting was greatly increased on his night drive home, and arranged to come back asap to remove the rest of the oxidization, ,
I would recommend if at all possible you buff each headlight as above, so you can see the depth of the oxidization, and also see where the oxidization is deeper and more intense,
Also I had a look at the 3M kits, and noted the small sanding / polishing disc pad holder,2" to 3" dia, and suggest that the 3m disc pad holder would be great for flatter surfaced headlight, like the red Ford Fiesta shown on other oxidizing thread, but as we know WRX headlights are not flat, and I would be greatly concerned the stiff, flat disc on the overall curvy WRX headlight, might cause even fine grade sanding discs to dig in accidently on the curvy WRX surface, again,
I still have grave concerns that I would not attempt to sand the beautiful curvy WRX with a 2to 3 diameter sanding pad,
Please consider this suggestion, which I will try as soon as I can,
That is to only use a full size buff machine with foam buffing pad, (which in my experience, does fit into and onto a curvy WRX headlight very well, it felt great, ) starting with a fine to regular buffing compound, to clean off the surface to visually locate the deeper patches of oxidization,
Once you are confident you know where the deeper patches are, change Velcro, foam buffing pad to medium firm foam buffing pad, and buff with a course cutting paint buffing compound to ( grind and cut with a course compound, not sand ) the deeper patches of oxidization away, ,
This should cause the surface to become slightly opaque, or cloudy,
Then go back to the regular compound and soft foam buffing pad to remove the opaque scratches caused by the course cutting compound, to again get a visual on any remaining oxidized areas, and repeat until all oxidization is removed, then use a fine foaming ( swirl remover, ) compound ( or dedicated fine plastic polish, ) with a new softest foam buffing pad to final finish,
I do think that a 2to 3 sanding pad on a flat headlight would work ok, but I also think a 7 dia foam buffing pads, with relative course and fine grinding / polishing compounds would be much faster, and above all safe for WRX headlights,
Good luck, and please take and post pictures of your resto,,