I'm not sure I understand what you meant about beginners doing all of it immediately. Do you mean they should be doing soft bags, harder bags, partner drills, and free sparring all immediately?
Yes, in principle; for example you say free sparring, but there can be set levels of contact and restricted areas. For example, just boxing, and nothing to the face. Also, it should be noted that the guys I train with are adults. As such, I see no purpose in
not exposing them to everything they will be doing; albeit, at lower intensity and contact levels. I never push them, or try to make them feel like they should do more. I train them for free, they show up we work out, we have a good time. Trust me, training once a week, it took them a while to withstand a full work out. But that's not what I'm talking about, going all-out right away. I want people to have an opportunity to test what I'm showing them, as I'm showing it to them. I've never been fond of conceptualizing to the point where people can become skeptical; I want them to see that it works.
Of course we're not even addressing shadow sparring and sparring drills. It's a progressive process, it's not like I'm just tossing them gear and having them go at it. In every session there should be warm-up: run, rope, shadow boxing, bag work, pad work; drills: upper body bag, upper body pad, lower body bag, lower body pad; combination drills: mixed combos on bag and pads; shadow sparring: no-to-light (and I mean light) contact, to focus on offensive, defensive and counter-offensive strategy--allowing you to try things without the consequence of getting hurt; sparring drills: like combination drills, but where both partners are throwing and blocking/slipping, so if you're off, there is a chance of being hit--again, light contact; and sparring: set contact and set areas. First the technique, then drill it 'till they know it, then explain how to use it, and let them try. That way, if they don't feel right about something, they are in a position to raise questions about it right away.
I have gotten way off-topic, and would like to apologize to the original poster. As to the original post; I'm not going to say that someone else's method is
wrong. If you want to condition your shins and don't have a bag, there are plenty of ways to make a home-made "bag." That's my suggestion; people say rolling stuff on your shins helps, but I've never had it do anything for me. Then again, I've been kicking bags since I was thirteen, lol. . .that might have something to do with it. I don't think rolling devices will condition your shins any faster than training, unless you're not training, of course.