i suggest a substrate of dirt. plain clean soil, no animal wastes or worm casting.
add leaf mould, sand, milled peat moss and it should great for your plants and so on. if you have a Home Depot, buy a bag of Super Soil brand potting soil, brown and yellow bag as it is just what you want. then in a ratio of 30% mix one/third of the other items to the soil and mix. black bag this for a few days in the sun and vola! dirt...
as for wood. i've been hearing the whole soak and bake idea but really you don't have too. imagine trying that with a four foot long tree banch that is 2 feet wide? heck! just spray it off well so no spiders and such remain and you're good to go.
also, i've seen in many of the cresty tanks that they seem enjoy a finer bark like a maple or ficus better then oak or other heavy thick barked branches. I've also noted the activity on branches with an average diameter of their waste and mid section more then larger or smaller sized branches. hope this helps.