Please let me preface the face that these are all GREAT questions (none of which are silly in any manner).
To answer your first question: IT really depends upon your needs for the particular model that you are working on.
- If you need straight pipes/tubes, you can use standard printer paper and roll the tube tighter that way. You can use toothpicks or bamboo skewers, and paint them to match the colour(s) needed.
- If you need pipes/tubes that bend (or are curved) you can use cardstock (or printer paper) and bend (or curve) to the desired angle. You can also use thin plastic covered wire (or even thin cordage) painted to match the needed part.
To answer your second question: I use a very sharp (brand new) #11 hobby knife.
- IF I am cutting out shapes that have angles ( i.e. squares, triangles, and other such shapes), I will start with cutting the corners of the shape first, then cut the lines to meet the corners (you get a cleaner outcome).
- If I am cutting curved shapes (i.e. circles, ovals, and other such shapes), I use small cuts all the way around the shape.
The answer your third question: It really depends upon the type of the reinforcing that is needed.
- With "wing" like shape objects, I will either use extra cardstock goes inside the "wing" and the mounting area.
- for areas that have "holes", I will add another layer (or as many layers as I feel is needed and what the space will allow) inside the part to make the part that has the hole.
- Adding layers to the inside of parts that will hold "weighted" components is also necessary.
Never apologize for asking questions. If you do not ask questions, how will you know what to do? If you do not know something, We want to you ask. That way, we can help you.