Fogged faceshields for many of us are a dangerous fact of life. Most of the "anti-fog" preparations work badly or not at all as is true of most OE faceshields which supposedly prevent the problem. "Pinlock" and other "double layer" fog preventers DO work, but they come with different problems.
I learned about Clarity Defog-it on webBikeWorld and recommend you check out their very positive review, as well as the comments from the dissenters.
Well, I just got mine today and am VERY IMPRESSED for what it does to prevent fog on my Shoei RF-1000 shield. If you decide to try it, you might want to follow the steps below which takes into account the advice from folks who were happy.
1. Remove the shield and soak it for at least 20 minutes in your kitchen sink using warm water and dish soap. Then use a SOFT cotton cloth to remove not only any external bugs, etc. but any other products you might have applied to the inside of the shield. Rinse and dry with a soft cotton dish towel.
2. To confirm (or refute) that this stuff works, you need a "before and after" breath test. If breathing on the shield doesn't cause fog, stick it in your fridge or freezer for a few seconds. Your breath should instantly fog up the shield.
3. Apply 5 drops of Defog-it to the inside of the shield and spread and polish it around with a microfiber cloth (not included but maybe important.) Polish only enough to eliminate any smears.
4. Repeat the "breath test." If it bascially worked with only small areas of fog, use a couple more drops and repeat step 3 on those areas. Repeat the breath test.
I have no idea how long this stuff works - if it indeed does work for you. Your comments, both positive and negative, I am sure will be informative.