There is only one reason to de-air resin: If it is very thick and the bubbles won't rise on their own. If this is the case, the resin had better have a really long working time so the de-airing process can actually be accomplished.
The best way I've found to get rid of surface bubbles is to coat the mold with talcum powder. Just dump some in, whack the mold around until you are satisfied the powder has come in contact with the entire surface of the mold cavity, then dump out what's left. You just want a very light coating, like it almost isn't there. Make sure no pockets of powder are stuck in corners or recesses. For most resins, this will do the trick and you won't have any surface bubbles. If this doesn't work, the resin you are using is thicker than most and you need to use a pressure chamber. However, a pressure chamber is useless unless you have de-aired the rubber before pouring the mold. Since you obviously don't have a de-airing chamber, your molds are not de-aired, so you're stuck. Try the talc. It cheaper than buying a lot of equipment. If it doesn't work, switch to a resin that is more viscous than what you are using.
One last suggestion. If the talc doesn't work, try again. Use the talc and once you've poured the resin in, dump it back out and let the mold sit for about 10 seconds. The put the resin back in. You're only trying to defeat the resin's surface tension, so in putting the resin back in the possibility of more bubbles forming is very unlikely.