Prepping model for priming

Nah. Especially using Comet. That leaves a powdery residue. And some surfaces, such as a bare metal finish, require the smoothest surface possible. Those paints reveal any scratch or blemish in the surface. 

Washing the sprues before assembly is not a bad idea, but is not a necessity.   if you do wash the sprues, be careful not to break any small parts or knock off any loosely attached parts that might then end up going down a sink drain. 

Washing yes, the rest, why bother.

I wash, build, tack cloth before paint, done.

I'll usually just prime and scuff with a fine scotchbrite and wipe down and paint.

Whether to wash or not depends a lot on the brand, and in some cases even the particular kit.  Stay tuned to other's build writeups.  Most large mfgs do a pretty good job of removing mold release, but there are still a few that are a bit behind in that.

Hey!

 I read that Mag religiously and never followed all their instructions to the letter.

      Specially that one. Didn't like the residue that the Comet left behind. Now I did use the Comet as a finishing rub before painting over the primer. Then Wash the dickens out of the parts you used it on!

       Now think. Mold release is not the problem it used to be. Finger and Skin oil from ourselves is the culprit now. Washed your hands ? Sure you did .And your skin replenished the oils you washed away.

       Test. Take a piece of your finest clear crystal. If you have some. Very clean! Now touch it. Go wash your hands and touch it again. Now come back in an hour and touch it again. You're gonna be surprised!

      P.S. still use the Comet, made into a paste, for final surface finishing on larger projects without lots of panel lines.

I washed sprues for a while but then realized I handle the parts so much between the wash and the paint it's sort of silly. Plus I try to remember to wipe down parts with damp ISO before primer anyway.

Re the etch attempt with the Comet, I use a good primer instead.

Prior to painting, or applying Bare Metal Foil, I spray the part with Simple Green and wipe with a paper towel. Then I spray the part with compressed air to remove any grit or fuzz.

I do all my filling and sanding then wipe with Isopropyl Alcohol. Then I prime and paint.

Jim   

Stay Safe. 

Damp ISO being Isopropyl Alcohol? 

Nope. Only kit's i wash are resin ones. Never had reason to wash a plastic one.

In in years of modelling plastic kits, I had to wash 3 kits with just soap and water.  The ones I had to wash were older eastern block kits.  They are not as bad anymore.  I have never got into priming of any type.  So sue me.  It works for me.  Now resin kits, it's  different story.  Lots of handling, lots of washing and priming.

Interesting, I started cleaning and leaving the sprues to dry years ago through hearing others talking about it being an advantage. Suppose it's become a habit, starting a new build soon looks like I'll be going cold turkey to see if I there is a difference. I like priming before painting will stick with that. 

tankboy51

In in years of modelling plastic kits, I had to wash 3 kits with just soap and water.  The ones I had to wash were older eastern block kits.  They are not as bad anymore.  I have never got into priming of any type.  So sue me.  It works for me.  Now resin kits, it's  different story.  Lots of handling, lots of washing and priming.

I always wash prepared parts by soaking in straight Simple Green, followed by a water rinse, and quick dunk in 91% alcohol to speed drying time.  Always done this, just as a matter of course.  In the case of large parts, I will also make a paste with comet and scrub the parts with a cheap electric toothbrush.  Using the same cheap eleectric toothbrush to scrub while rinsing gets the comet residue off.  Might not be necessary, but it hasn't caused me any problems either.

For priming, I always have a jar of decanted Tamiya grey surface primer ready to shoot from my airbrush.