Is your truss design taken from a commercial truss? A lot of commercial trusses use higher grade lumber than is generally found at the big box stores, be careful you use the correct grade. As for the truss brackets and nailing, you may be able to find some information at the University of Wisconsin Forest Products Laboratory website on gusset design and nailing patterns. Before the introduction of air impact gang nail systems, trusses were successfully built using plywood or similar gussets, and the data to build them must be available somewhere, even though the technique is no longer followed by any of the commercial shops I am familiar with. Frankly, getting an engineer involved on something like gusset design seems to be overkill, kind of like hiring an engineer to design standard framing for a house, it just isn't necessary unless there is something unusual about the framing. Ditto for the trusses.