I did a race like that a few years back, spent more time cleaning, inspecting, repacking and replacing parts.....yea I got a 3rd place in class, nice big huck of plastic, but sent 4 times the entry fee repairing the bike.......fun factor was super high, but the after math was a mess!
I use a foam pack under the skid plate to keep mud out, jammed into every place I could put it.
This sounds crazy, but if you ever race a really muddy event again, put some womens panty hose over your radiator luvers........

It works!!!
Take the plastic luvers off, then find a leg opening and work a leg around the luvers, then tie a knot so it does not come off. Do each side. You want it tight, but not to the point to tear it.
If you use a "nude" color no body will know it is there!
What it does, allows air and water to flow through, but will not collect mud. The nylon is super slick, mud will not stick to it, thus not plugging up your cooling system with mud!
I have also taken off the front fender and covered it before as well. We all know how much mud will build up under the fender, just tie the knot at the back of the fender.....yea, it looks crazy, you might get a few looks, but it is totally worth it when you don't have 3 pounds of mud collected under the front end!
When your done, take a razor blade and cut the panty hose off.......
I know it sound insane, but it REALLY WORKS!
A mud race is all about prep work...more like combat, trying to keep that stuff off the bike.
I have tried WD40 under fenders.....washed off if there is a alot of mud puddles.
I've used Pam cooking spray under fenders as well, worked better, but clay is a pain in the butt to keep from sticking...again the panty hose works the BEST!!!!!
I also duct tape where my visor meets the helmet and also all the "venting" in the visor. This keeps water from dripping into the visor area from the top of the helmet, with a overall result of trying to keep goggles clean.
Also you can take some plastic and duct tape a extention onto you exisitng visor, it helps with water and if your getting roosted you can dip your head and the extenion will block more roost, and help keep goggles clean.
Rolloff systems are great as well Scott Works system with the dimples on the lens will keep the film from sticking to the lens. It allows water to pass, but no to stick.
If your handgaurds have air vents, tape them up, to keep mud and water from passing through the vent holes and onto your grips and gloves!
Again, prep work is the key.....too bad you'll spent more time doing the prep work than really racing!
Sorry, did not mean to hijack your thread!