I just use 2" wide coloured tape to fix the spars etc in place. In the UK I get it from Staples, a stationary shop, it is sold as packing tape in a variety of colours ..You should stick about 1" of the 2" all along top edge of wing, leaving the remainder loose, turn wing over so you have the sticky side up, place the spar along the edge as tight as posible, then wrap the loose tape over and stick it to the wing..benefits 1...easy removal of spars without being covered with glue. 2...It also stiffens up the depron. 3..depending on the colours used this can also be the models decoration. 4 ...its quick!
On the vulcan the wings leading edge shapes are stuck on similarly, using 2" top and bottom, that now equals 2 layers of tape, even stronger and stiffer,
The elevons are similarly hinged, another layer, but have care to fix the tape with the elevons bent in the oposite direction to the side you are sticking the tape to.... if you dont do this the elevons will not move at all.
I also tape all leading edges with 3/4" clear tape to prevent rips in the depron if you catch anything in landing.
More tape on bottom of fuz for same reason
I then coated the depron and tape with an almost clear primer which gave the coloured acrylic paints something to stick to. for this I used a Pactra sealer bought from my model shop UK.
sorry if I keep pluging that blue motor, but it really is that good, £12-15 in the UK and better performance than my axi 2208/34, less weight, less current drawn, enough thrust to easily fly the vulcan at 1/2 power..
now less than £8 from robotbirds.co.uk
I forgot to say, my vulcan was built with 3mm depron. the wings bounce a bit in gusty conditions but it is more than strong enough for any manouver I can do...

It also looks great in the air.
Test flights are absolutely no problem, landing is a doddle, you can raise the nose high and come in at a crawl, with a slight breese you can harrier it to the ground.....