Seriously, don't waste money on parcel services. I have an online business and regularly ship to Germany from Odessa and never have any problems with the Ukrposhta. 3kg will cost you about 600UAH++ and takes about 7-14 days to get there. Put in a box, pack well. You will need a customs form, to EU there are 3 copies needed (get them at the counter of the post office) plus the "white sheet". You can just take the boots to most main post offices and they will even sell you a not expensive box and pack them for you. Fill out the form there at the post office and send.
Keep in mind, you need to put low value on the declaration, as in Germany, whoever picks them up will need to pay VAT on the item value PLUS the price of the postage. Be sure to put "USED" in the description, "FOR REPAIRS" would also placate the Krauts...