how to instantly train in fallout shelter

So, it may be more beneficial to build 3 block training rooms and try to have 6 dwellers training at once, vs paying for all the upgrades. Whereas having a tier 2 room with 6 dwellers in it vs just 1 dweller going from 9 to 10 is a savings of just shy of 2 hours. I haven't been able to find any greatly detailed or thoroughly researched numbers, but based on this reddit post and accompanying spreadsheet going from stat 9 to 10 in a tier1 room vs tier3 room is only a savings of 1 hour 18 minutes. That being said, from what I've been able to find, it seems like the # of dwellers in a room training at the time may have a larger effect than the level of the room.

Especially once you realize that having a Dweller's Endurance maxed out BEFORE they start leveling up drastically increases their hit points and start trying to max out level 1 dwellers before sending them to any tasks. Later on, with large vaults, I'd say time is more important than money, and every little bit helps and are well worth upgrading the training rooms. Again, upgrading training rooms wouldn't have any effect, other than making me 50-100k caps lighter. However, more than half of my dwellers have full SPECIAL now and training rooms are half-filled, at best. Perhaps, now might be the time to upgrade some training rooms. I have some 700k caps now, and I really don't know what to spend them on. So you should be really only updating those if you have some ungodly amount of CAPS and it's burning a hole in your vault.

Other rooms have very similar (though not identical) numbers. Just to put some numbers here: Strength Level | Base | 1st Upgrade | 2nd Upgrade

How to instantly train in fallout shelter