raw-al, my tongue has been constantly coated for years
It seems safest for me to just avoid the milk.
That's very likely to be a cause or maybe the sole cause.
What I suggest is sip very hot water all day, till your tongue is consistently pink. The water should be as hot as you can stand without burning yourself. Just tiny sips.
You'll find that you will drop 5 to 20 pounds from doing this, as the hot water will tend to warm up and hydrate the body and specifically the GI Tract, increasing blood circulation and softening and liquidating old crap ( technical term for the overused word "toxins") from the lower GI Tract and thus motivating it out of your system more quickly than it would normally.
You'll also notice an increase in urine and it may be dark initially, which means you are downloading "stuff". (another tech term) You'll also notice an increase in defaecation therefore making you feel lighter and more awake, energized and clear minded. You feel this way because now the intestinal walls can get access to the finer products of digestion that includes nutrition for the brain etc.
The faeces may be strong smelling and in various states of liquidity initially, as you expel stuff you've been storing on the walls of your GI Tract for longer than you can remember. I've heard stories of people expelling multicoloured, disgusting stuff along with gas.
Funnily enough often people get the impression that they have gained weight when what has really occurred is that the crap (tech term, doctor speak) that they ate is rotting in their gut, because it is indigestible or there is too much in there, so the peristaltic action of the GI Tract cannot move it around to mix the various digestive fluids into it, to actually digest the food. It could also be that the foods that have been eaten are reacting with each other causing gas. This gas causes their lower abdomen to puff out, so it looks like weight increase.
A classic case of this is eating fruit after a meal. The fruit digests very quickly then sits on top of the other stuff and just bubbles in reaction to the digestive fluids. I suspect cooking food makes this worse.
If you find the coating returning, you are doing something wrong, so eliminate things from your diet till you find the offender.
Some people do this all day, as a habit, (drinking hot water) which I am not sure is necessarily a good idea. If your tongue is pink, that means your digestion is healthy and so continuing to drink or sip the hot water may cause issues in the opposite direction.
This is the difficulty with "internet diagnosing", people taking things to the extreme. "If a little is good then a lot is better" is the resulting thought process with some leading to other issues.
You can also use things like Triphala to clean the system and it works gently and well. Castor works gently and well if done properly. 1 tsp or more before bed. You can do this for a long period if you wish but not more than a month. Tastes gross but works well. : )
One other thing is that the tongue should be pink
not red. Red means something else. A pale colour indicates anemia.
It is a good idea to scrape your tongue, but you should do it first thing in the AM after awaking and before eating. Doing it before bed will stimulate the organs and make sleep difficult.
More info is available from some of Dr. Vasant Lad's excellent books starting with "Ayurveda the Science of Self Healing"
http://ayurveda.com/shop/science-of-self-healing.html and "Volume 2 Textbook of Ayurveda".
However if you are eating properly and raw paleo you shouldn't need these crutches.