1) IF you opt to use any sort of creams (vaseline is NOT a good choice), you put it on YOURSELF, not the chamois. However, unless it is so hot that you are sweating profusely, or unless it is pouring rain, you should not need any sort of creams on rides of less than 100K. I use Ozonol in one tiny area of me, and a non-zinc diaper cream on the odd occasion when it is hot or wet.
2) As mentioned above, skip the creams altogether unless it is very hot or very wet. You don't need them! All they do is to provide an extra layer of protection over your skin in conditions when your skin is extra fragile, such as when it gets wet.
3) For any lengthy tour, it is a very good idea to have two pair of shorts.
Incidentally, when I toured through Australia for 3 months, I frequently went 5 or 6 days in the same shorts without showers and without washing the shorts. You get used to it after a while. Then I'd change shorts, and wear my second pair for several days before we'd finally arrive somewhere where they could be washed. I rarely used any sorts of creams, and I did not develop any saddle sores at all during that whole time.
If your bicycle is set up correctly, and if you have a good saddle, you shouldn't have any issues (or certainly not significant ones) with your contact points (hands, butt, feet). In fact, if you've got your bicycle set up correctly, and if you've got the right saddle, you could ride in any kind of shorts, or whatever, without problems. I've done a few 80 km days in the heat of Queensland wearing a bathing suit and beach shorts with no saddle sores or any other discomfort. Bicycle fit is VERY important!
IF you happen to start to develop a saddle sore, put a little bit of zinc oxide cream on it (found in the baby department of your local department store or pharmacy) just before you go to bed. By morning you'll be fine.
BTW - have you had a look over the packing list link I posted? It is extensive, and includes pretty much everything anyone would want on a tour. You might not want to carry all of that, but it might give you a good idea what sorts of things cycle-tourist do take with them:
http://www.machka.net/packinglist.htm