Yeah should be fine I don't use flux for quick connections. What do you mean long? Length of heat time, wire length?
Length of heat time is always just enough to do the job. Try to get the smallest diameter solder possible for your driver connections. I use .022 Since your module has pre connected leads, you shouldn't have to worry about overheating the diode.
As for the length of the leads, just enough so they will tuck in, but not so long where they will be a tangled mess inside the host.
Does that help, or am I missing the question?