The following way you can solve your issue.

1. Set custom field on sale.order and stock.pirking in py as well as view side.

2. Inherit the stock.move in your custom module and use the _prepare_picking_assign() over ridding method.

3. Using super and set your custom field value.

4. View that changes After confirming of Sale Order document.

For example :

from openerp import models, fields, api, _

class sale_order(models.Model):

    _inherit='sale.order' customer_field=fields.Char(string='Customer Field')

class stock_picking(models.Model):

    _inherit='stock.picking' customer_field=fields.Char(string='Customer Field')    

class stock_move(models.Model):

    _inherit='stock.move'

def _prepare_picking_assign(self,cr, uid, move, context=None):

    res=super(stock_move,self)._prepare_picking_assign(cr, uid, move, context) if move.procurement_id and move.procurement_id.sale_line_id and move.procurement_id.sale_line_id.order_id:

        sale_obj = move.procurement_id.sale_line_id.order_id if sale_obj.dif_pick_address:

            res.update({ 'customer_field':sale_obj.customer_field, }) return res

Above code is working fine in Odoo 8.0 version

Also, You should set in the view part so that you can check the sale order values come into stock picking after confirming your sale order.

I hope my answer may helpful for you :)

Source :

http://stackoverflow.com/questions/39953729/add-shipping-address-field-in-stock-picking-in-odoo/39956194#39956194