There is quite a large industry devoted to providing instructions, materials and various size and quality "kits" to build a mission. There are at least three approaches to consider:
1. Buy some form of a kit or cut-out template. Bellerophon Books sells a large (about 2’ long x 10” wide) item called California Missions Cut Out Book (in two volumes) (San Antonio is in Book II). These are pretty simple drawings. The paper on which the mission outlines are printed is regular paper so most model builders use this drawing as a template to cut-out a cardboard version of the components. You can then paste the template on to the cardboard, or draw the lines yourself but whatever approach you take I would think you would want to color the end product. Our website has a Visual Journey of this mission that includes several photos of the church…which will give you a good sense of what it looks like. There is an online source of paper models and templates from Paper Models Inc. (www.PaperModelsInc.com ) These look pretty neat. They have models you can download for all 21 missions.
2. Another approach is build a model using detailed instructions and guides. It could be made out of cardboard, building blocks, Styrofoam, clay, salt dough or even sugar cubes (a material our family has used for models with good results). Roof tiles can be made by gluing elbow macaroni or rigatoni to cardboard and then painting them a brownish red. There is a book Projects and Layouts by Kari Carnell and Libby Nelson that goes into considerable detail on the how, materials you can use, sources etc. It is about $22.00. There is also a lot of “how to” material on the Internet.
3. The ultimate approach to model building is to do something original, using more detailed and accurate architectural drawings. This lets you do something more refined and detailed than a typical model kit, which simplifies the elements a lot. This approach has led to some pretty realistic and captivating models – some of which are so good they are on display in mission museums. (One strongly suspects the parents that were involved were artisans, architects or just creative people who made this into a major project to complete with their son or daughter). Most of these “ultimate” models utilize original drawings. On which turns a tale. In 1933, during the Great Depression, someone had the idea of providing work for unemployed architects and photographers by having them document historic buildings. They employed 1000 architects that year in the project, which has given us a priceless legacy of really detailed drawings of many historic structures including some but not all of the old Spanish Missions (fortunately San Antonio was one of the missions still standing at the time and it is fully documented). These drawings and a ton of black and white pictures are available online (free) at the American Historic Buildings site of the Library of Congress. Here is the link:
Just type in San Antonio de Padua. Of course, this being America some entrepreneurs have packaged a sample of these drawings and sell them in a book entitled California Mission Measured Drawings. I am enclosing a copy of one of the seventeen drawings of San Antonio and it architectural features that are available online.