My experience using Sig dope is as follows ___

The Sig dope purchased at a hobby store as it comes out of the containeris thin enough to be brushed on easily without any dilution (wihout adding thinner).

The number of coats needed to fully fill the weave depends (of course) on the thickness of the fabric.
I recetly used fabric 0.005 inch thick as measured with a Mitutoyo caliper and counted the fabric threads to be 80 threads per inch. ( About 60% transparency)
More than 6 coats of dope were needed to fill the fabric,
Note that the posting by cutaway says "to fill the weave some" which means not fully filled.

Two coats of colored butyrate is rarely sufficient to give a nice colored finish particularly if you wet sand the coats with 600 grit (or finer) wet paper and finish with "wet coats" of dope. Wet coats here means diluted dope just enough to let the dope flow as an even thickness without runs before it start setting (curing, drying).

For me 5 or more coats of colored were necesssary.

There is tautenng and non-tautening dope as labelled by some supplier or manufacaturer.
My experience is that I have never seen dope that does not tighten.
I think it is a matter of degree. Aero Gloss, Berry Brothers, Sig, Randoph, all have thightened nicely and keep doing so for ever. Some 50 year old planes are still "tight as a drum".

Zor