Judging from the pictures posted on the castboolits forum, the ES gun method gives the most consistent and smoothest coats.  If one is going for absolute best accuracy, my guess is this would be worth the extra effort. 
I have read that most are getting better results ( with all methods) with polyester based powders as compared to resin based ones.  Whatever powder you use, make sure it is stored in airtight containers so it doesn't "clump up" from the humidity in the air.  (Another use for the phrase "keep your powder dry".)

Jeff

I use a Lee push through sizer and size AFTER coating. 

When needed, I open up the sizing die to fit the bullet to the specific barrel.  The sandpaper wrapped around a straight steel rod, inserted through the die and rolled on old short napped carpet method has worked very well.  I think I have started with 120 grit and finish with 400, cleaning the die and running test bullets through it as I go.  (To make sure the die turns when I roll it on the carpet, I put two or three die lock rings together like a lock nut, on the die.)

Some size both before and after.  I am trying to simplify, and  to minimize my effort and time investment.  I am trying to "work smart, not hard". 

Although In my twenties I could head shoot cottontails at 40 yards (200 grain RCBS semiwadcutter over six grains of Unique from a Colt Gold Cup), my now 61 year old eyes force me to greatly lower my accuracy standards.  Powder coated bullets may or may not be as accurate as conventionally lubed cast slugs - I DONT REALLY CARE, because I am not accurate enough anymore to find out!  The method of coating I now use might possibly not produce as even a coat as more time consuming methods, but it is good enough for my needs. 

Everything I know about this I learned from the guys and gals on the cast boolits forum.

Jeff

New guy to this forum.  I like what I have seen so far.
I am not an expert, but I believe I can make life a little easier for those here who are powder coating their cast bullets.  Most of what I have learned is from the "cast boolits" forum.

1. Buy an oven thermometer to be sure your toaster oven actually gets up to the usually recommended 400 degrees. Just a few bucks.
2. Convection ovens help eliminate hot / cool areas.
3. NONSTICK aluminum foil works. Make sure you put the bullets on the nonstick side.
4. Now for the biggest time saver: use your vibrating brass cleaner for applying the powder. 
     I put up to 200 or more bullets (9mm, .40, .44, .45) in the vibrator (after I clean out the brass cleaning media) dump a couple tablespoons (or more) of powder on the bullets, put the lid on, plug it in and walk away to do something else.  Ten or fifteen minutes later, I dump them into a wire basket I made from 1/4" screen ("hardware cloth" I think), which is inside a 9x12 cake pan. Lift the basket and give a few easy sideways shakes, and excess powder falls into the cake pan, to be used on the next batch.  I put the wire basket directly into the preheated oven and bake 'em!  Yes, they are in a big pile, actually touching each other!  When they are done baking, I remove the basket of bullets (wearing leather gloves!), dump the bullets into a metal tray and immediately stir them around with my gloved hands to break apart any that are touching. 

This is WAY quicker than shaking them in a Cool Whip container and placing each bullet onto the baking surface.  Yes, I lose a few that are stuck base to base (they just get re melted), but the time and labor savings is well worth that small sacrifice.

I have not coated rifle bullets, but for handguns, this works very well.

When you are done coating and go back to cleaning brass, you will need to clean out the powder.

Hope this helps someone,
Jeff