I put the slugs on myself, but at work I have access to the commercial sewing machines and materials needed. Yes, the boltrope remains: the slug attachments are simply "wrapped around it" ...
The slugs themselves were very inexpensive. My "main" problems are with *raising* it, not dropping it (as long as I clear the halyard running end 1st), as I'm usually hove to when I raise it, and if the boom is out too far, the topmost batten will get stuck under the area where the shroud meets the spreader. 'Course, that's an issue I had anyway before I put on the slugs and was using the boltrope. At least this way, I can use one hand to pull on the halyard and the other to guide the leech around the shroud/spreader area, and I don't need a 3rd hand to feed the boltrope into the slot ...
For anyone who's considering installing their own slugs, or just advice to the sailmaker if they're not familiar with the DS: the lowermost slug should go just above where the sailstop is, right above the feed slot in the mast. Also, consider where the slugs above that are when reefed.
AND, if you go the slug route, ALWAYS have a spare slug stop onboard, as those things are like Mexican Jumping Beans: when reefing, they'll get knocked out of your fingers, bounce off the cuddy roof, and fly overboard at the drop of a hat! Don't ask me how I know ...