Tin and silver finishes have been widely used for both surface mount and through hole components for many years due to their slow oxidisation characteristics and therefore long shelf life. So the simple answer is that you can use the same pot and solder iron temps that have always been used.
When the molten solder from a Sn/Pb pot comes in contact with the higher melting point lead free metals on the components they will melt and dissolve. The pot temp used will be around 245 - 255 for Sn/Pb which is higher than the 232 temp of the highest metal finish (pure tin) and will cause localised melting. Also the solder dissolves the surface of the component much in the same way as it would the copper finish on an osp board, The copper melts in excess of 1000 degrees but still solders well most of the time.
The whole solder process relies on metal dissolution and chemical bonding to work not melting.
Solder Irons remain the same for the same reason and also because they are at about 380 centigrade. Again this is plenty of heat to melt a lead free alloy. What we have found in Europe is that even with lead free wire that you can keep the same temperature but reduce the diameter of the wire to the next available size down. This ensures that there is no increased risk of temp damage to the components around where the hand solder process is taking place and the soldering speed is the same.
Douglass Dixon is the Chief Marketing Officer for 360 BC Group, a marketing agency with offices throughout the US. 360 BC specializes in consulting and implementing successful marketing programs that utilize the latest in marketing, sales and technology strategies. As an electronics veteran, Dixon has worked in the industry for over 30 years for companies like Henkel, Universal Instruments, Camelot Systems, and Raytheon. Dixon's electronics industry experience includes a broad skill set that includes engineering, field service, applications, product management and marketing communications expertise.