yes, benedryl is an excellent choice. it is a substrate of 2D6, the minor metabolizer of hydrocodone, and the major being 3A4. so by taking it 30mins-1hr before your dose, it will act as a potentiator of sorts not only by its effects on the CNS, but also because it will occupy and clog your 2D6 enzyme. in turn, your high will last longer.
i wouldnt start double dropping now if i were you. even after a couple years of experimenting with opiates, i still get noticeable effects such as euphoria from my second dose of the day. however, i try not to take oxy/hydro more than once a day and 1-2 times a week.
if i were you, i would wait another 1-2weeks of taking the hydro daily before you increase your dosage because tolerance is a hard thing to reverse. make sure you always take your hydro on an empty stomach, and if you want there are multiple OTC medications that will help with pain and increase euphoria. benedryl as stated before, and DXM will both help the high so to speak, and naproxen sodium (aleve) will help reduce your level of pain. tagamet and white grapefruit juice are also OTC and will clog your enzymes like benedryl and increase the duration of hydrocodone's effects.
DXM is my favorite potentiator though, behind tagamet. it is a substrate of 2D6 and 3A4 which kicks ass. i also hav ebeen taking 60-100mgs daily for reversing tolerance and for its intoxicating effects.