I haven't used silk since the "good ol' days" and much preferred nylon at the time to silk. But one thing I learned, when filling the pores on silk (or nylon) on open bays as the wing is to brush from the underside. Hold the wing level and brush the first coats of clear on from the underside. This way, if any puddles form, they will form on the bottom or outside of the covering and you can brush over them again to remove them. Use relatively thick and fast dope at first (Brodak would be an excellent choice--something that wasn't available to us then) and wait until it gets pretty sticky before turning it over to do the other side. Once all the pores are filled, you can wetsand and then use thin coats to spray whatever other finish you plan to use.
With silk you MUST use plasticised dope. If you don't, with the first "whoops" the entire covering job will shatter taking a portion of the airframe with it.
Now, with the plasticised dopes that are available to us today, you do not nearly need to be so afraid of silkspan, either. I cannot recall when the last time was that we punched a hole in silkspan just by handling it. We have crashed a plane--nearly straight in--with the ribs hollowed out to about 3/16 all around, and, although the wing folded in the middle, the rest of the wing remained intact. In the "good ol' days" it would have been totally shattered, totally destroyed. With the plasticised dopes you can "thump" the center of a wing panel with your finger and you won't hurt it. And you only need medium silkspan to do this. It is lighter and takes less dope than the heavier stuff, and it finishes lighter than the light stuff as it takes less dope to fill the pores. A good silk covering can get extremely heavy when you have to fill the thickness of the weave. Matthew will add typically 6 to 7 ounces starting with a bare airframe and covering it, doping it, clearing it, adding inklines, more clear, and then buffing it out. His planes have moved progressively towards the front in appearance point judging the last few years, landing in the front row at this year's nats (Thank you judges). This plane had over 200 flights on it before it reached the Nats. Last year's plane was too new. It had only 7 patterns on it before coming to the Nats. But he pulled it out again for a contest earlier this year at Muncie by which time it had over 400 flights on it. One of the judges asked if it was a new plane. Matthew replied "it was last years, but it was young yet since it had only a little over 400 flights" and the judge asked what you may ask, how did he keep it from getting dings and dents. It is simply a matter of how you handle it--very carefully. You can do a silkspan finish that is light, durable, and long lasting. Don't be afraid to try it.