I have never covered with tissue but I do use Sig Koverall fabric.  Instead of dope I use Minwax Polycrilic.  It is water based and very light as all the water evaporates when it dries.  It dries in less than 30 minutes and it takes about 6 coats (sanding between each coat after coat #3).  You do have to paint the model as the Koverall is white and the poly is translucent.  I dont know if this method will work for what you are trying to accomplish but it may be worth looking into.