I am afraid, short-cuts never work out satisfactorily ...
There is no way around tying a few knots at this relatively large scale. This Forum seems to focus mainly on late 19th and 20th century ships in small scales. So you may want to have a look e.g. into
www.modelshipworld.com, where several USS CONSTITUTIONS and other contemporary ships are in progress in various scales. A lot rigging details and techniques are discussed in that Forum.
As for the decks, you may want to (super)glue a piece of wood lengthwise or across to take out the warp, if that can be done without being visible. It is also possible to put polystyrol parts into hot water and then weigh them down onto a flat surface while still warm to take out some of the warp.
wefalck