Fightfighting is useless. Camo is probably the most useful overall skill as it is in constant use. I go Camo -> Repair -> Firefighting on every tank I own.
Often, if I'm moving the crew over to another tank, I won't select a secondary skill. My T29 crew were 100% for a long, long time before I unlocked the T32 and I didn't pick a secondary skill for them. I used the 20,000 credit crew re-training option and they started off at 100% in my T32 plus I selected my secondary skill which started out at 75% for them.
ie. Don't immediately select a skill when one is available if the crew is going to be moved. Holding that back until you re-train the crew means that they will transfer at 100%.
I started in my T32 with the upgraded tracks, upgraded turret, 105mm T5E1, the best engine and the radio upgrade, with a 100% trained crew who possessed 75% camo skill each. (free exp + patience)
Hmm is camo really that useful though? I know these values are old, but I don't see WG increasing the camo values on big ass tanks:
www.wotdb.info
If you right-click on a tank and click "more info" (when available), you can see the camo values. If you're looking at an enemy tank w/camo value C at a distance D and you have detection range R, you will detect them if R >= (1-C)*D (assuming no obstructing obstacles) or if D <= 50m. (Note that R can be bigger than 500.)
Stationary US heavies have a camo value of almost 0.2. Stationary German heavies have camo values of more like 0.03. Even the bigger german mediums only get up to 0.07. (Compared to 0.3ish for most countries' mid-tier mediums).
Additionally, crew camo (like the camo net) is a multiplicative bonus. I don't know exactly what that bonus is. So if crew provides say a 10% bonus and your base value is 0.6 (mid tier TDs), then you're now at 0.66--nice. But if your base value is 0.03, then a 10% bonus puts you at 0.033. Useless.
Well, useless on paper anyway. Maybe more experienced players here have some input on whether it had any effect. But this is why I'm wary of getting camo for my VK 3601 crew. It'll be useful on the 3601 and the 3002DB, but it won't help me much on panther on up. So yeah I've heard firefighting sucks, but on the German tanks I'm headed toward, camo might be crap too
Caveat: I know those camo values are old & WG has adjusted tons of camo values/mechanics in 6.4 or 6.7ish. So if y'all know camo is useful for panther/pantherII/e-50 then by all means lemme know and then ignore my statements, haha.
And yup I knew (and forgot) about the extra XP transferring into the primary skill. I imagine going from 90->100% primary skill for free is way more useful than having like 2% more in some secondary skill.
Visaoni: Actually no, that's not what happens. When you re-train, this is how it breaks down:
1) Unless you spend 200 gold, primary skill is reduced by some amount (e.g., same class of tank, pay 20k credits: reduced by 10% to a minimum of 75%).
2) Maxed out secondary skills are completely unaffected. If I had a 100% crew in a T-29 with 100% repair (and 0 additional XP) and I retrain for T-32, I will get a crew at 90% primary and 100% repair.
3) Let's say I have a 100% crew with 100% repair and 50% camo. I also have 5000XP toward getting 51% camo. After the transfer, I will have a 90+% crew with 100% repair and 50% camo with 0 XP toward 51% camo. That 5000XP, unallocated XP falls into the primary skill, boosting it.
4) If you have extra XP & no assigned skill, then all of it can fall back into the primary skill as indicated by Elcs.