If you are using a eutectic solder alloy "cold" joints are much easier to avoid. The solder goes from melted to "frozen" without a "slushy" phase.

Sucking the solder off of the tab to reveal the hole is ideal. If you are lazy, as I typically am, and don't want to pull out any extra tools I will just heat up the tab with my iron until the old solder melts and probe around with the wire until it goes through the hole (also trying to knock out any old wire that maybe stuck in the tabs hole).

You can put a little fishhook bend on that wire once the solder freezes and repeat the process with the next wire. Hopefully the fishhook bend you put on the first wire keeps that wire in tabs hole while you try and shove in the second wire.

If the joint looks marginal after the second wire goes through I will put a fishhook bend on that second wire and reheat the entire joint and add in some new solder since I now have my other hand free to add solder instead of having to hold the wire in place.

You can get into problems if you are working a new machine that has some weird lead-free solder. Combining different solder alloys can make the solder act oddly. I would recommend you use a solder sucker to remove any of the old solder if you having problems with the solder not flowing right. I am sure someone can chime in with what vintage of pins have this type of solder. If you are working on older pins like I normally am, all of the solder appears to be leaded and compatible with the eutectic tin-lead solder that I like to use.

I hope that makes sense.