Here's how I do it:
The more you can solo the young ones the better. When you start running them with other dogs, first take your slowest and truest running hound and brace them together (that is, run them as a duo). I try to run a pup solo at least 50% of the time. I hear you about being limited on your running because of work. I am in the same boat so I don't have the time to solo my derbies (first year hunters) as often as I need to. I would recommend you find a starting pen and pay somebody else to get them started for you. Most guys charge around $40-$80 a dog, depending on where you are and how long it takes them to get them going. You will get back a dog that can circle its own rabbit. Then you are over the hump.
With young pups it takes tons of tracks to get them started. A starting pen can get your dog started in as little as 2 weeks, then you can take it from there. I have started dogs before by just taking them out with my other hounds once a week and it can take months for them to start. If you can swing it, a starting pen is the way I would go.
At 6 months your dogs are probably ready to start. If you take them out with your pack and they start getting interested in a track but don't really go, that means they are probably ready.
I am always very careful about how much pressure I put on a young dog. I have a derby now that I have very big expectations for. She looks like she is going to be awesome, so I am super-babying her around my pack. I want to put a little pressure on her and get her to run with the big dogs and I hate leaving her at home, but too much pressure on a young pup will ruin a dog.
Biggest thing is, be patient with the young ones! They will drive you nuts acting like puppies and being goofy in the field. A lot of excitement to see how they turn out though!
Would like to see some pics of your pack and pups! Welcome to the forum!