laboratory maps serve as good ets for that value guide of prices can be found here: http://www.sunnyneo.com/lab_map_prices.php
100k-150k, buy a some ETS medicines like Cactopis Cream from SW 150k-200k, buy Bubbling Fungus for 130-150k from trading post. Or buy snorkle snouts for any price within this range 250k-300k, buy Bag of Peanuts from tp For medicines, just sell them in your shop. For bubbling fungus, sell it at the battledome chats or just put in tp (BDers will offer). For Snout and BoP sell at avatar chat boards
Paint Brushes are also ETS. If your making deals that are well into the millions you can use Baby Paint Brushes and Royal Paint Brushes!
I would use baby pbs. buy em at 590,000 and sell them at 589,000. They sell super fast. Bag of peanuts aren't bad either for around 250k - 300k trades.