1) in your accounts the expenses would go to "packing charges" , no cenvat credit available in this case, as the goods are not manufactured by you.
As you are not direct manufacturer nor the duty is paid by you on finish goods so the input credit is not available to you,
2) you can send the goods to next supplier on plain challan, make 4 copies of it, in follwing manner, mentioning specifically " goods not for sale - to be used packing of goods against our order no ............................. and returned to us" without charging any excise or vat/cst.
copy 1) to be retained by the receiver
copy 2) signed and delivered after receipt of goods at their end
copy 3) singed and returned alongwith the materials, with a note that goods are used in packing of goods and returned to you.
copy 4) extra copy, may be used to produce with their invoice.
specifically you have to take records that the packing goods are bought by yourself, sent to next party , returned back with goods and cleared with principal goods, otherwise u will face trouble in vat assessment as the goods would remain in your custody(stock) and vat department may consider it as undisclosed sales, so consumption of these packing gods in the goods.