Richard,

body filler is typically a polyurethane based material - it shouldn't be porous. It is also rather hard once dry although sometimes brittle depending on the brand. The glassing of wood is to give it a hard shell and to seal it so that the paint doesn't keep being sucked into the wood grain. If you apply body filler atop a glassed model (very typical) you don't need to reglass the filler. Whether you "glassed" with glass cloth or carbon veil makes little difference.

Once your model is glassed and you've applied filler here and there for a uniform surface, you can proceed to prime. Some will even glass and then apply filler everywhere which is then sanded off to only leave the filler in any remaining exposed grain. I wouldn't add any further "clear" coats - no need for them. I'm sure Bill does and excellent paint job but I believe he is rather unique in using clears such as urethane before using primer. When priming, I recommend you use a thinner sandable sealing primer. Once applied, the primer will show all the blemishes that you thought had taken care of on the model. Use body filler where these are found and then wet sand the sucker down with 400 grit until the model looks like a nasty mess but feels very smooth. Repeat if necessary. Once your surface has one or two coats of sealing primer sanded down, you can apply one or two coats of high build primer, again wet sanded in between. The final coat of primer before paint (whenever you reach that point) wants to have a little tooth so don't sand it down too smooth or the paint won't hold. Depending on the colour scheme (i.e., if you are using white or light colours as a base colour), you might need to top prime with a white primer to provide uniform color tone to the color coats.

If you have a paint gun and want to try a light paint finish, you might want to go with water borne products. Heck, you can even shoot household latex paint with a little care and prior practice. It will look somewhat dull and/or mat once applied but when you apply your final top coat, the colors will really pop if you use a gloss acrylic urethane. If you take a look at Jeff's scratch built Aurora thread, you'll see how he did this with latex water borne paint. Here's the link to where it begins:

http://www.rcuniverse.com/forum/fb.asp?m=7097957

Just some suggestions,

David