I've got nothing for the sand boa, however switching the BCI shouldn't be too much of an issue. They aren't exactly known for being picky. I suggest giving her a couple more weeks of proper husbandry and then trying a f/t rat instead of a mouse (you said she was on rats before right?). It could be a preference thing, but generally, boas switch from live to f/t fairly easily. Just try and stick with the same type of rodent.

I might just be extremely lucky, but I seem to have no trouble getting all kinds of snakes over to f/t. I thaw them out in a bucket in the room with the snakes, so they smell it and start exploring before I even offer the food. I make sure the rodents are really hot when I first offer them as this helps get their attention (of course you don't want them to be so hot they can burn!) I've also tried one other trick... I give the snake a small live prey item and as they are swallowing it up, put another prey item (that is f/t) in the mouth so they take it. Almost every snake I've tried this with switched within the next 3 f/t attempts. 95% of my collection is on f/t and I haven't had to use any other methods. Some snakes prefer you leave the prey on the tub floor but most seem to take it better from tongs. It just depends on the snake really. Good luck.

The sand boa, if it is healthy and a typical sand boa, will eat whatever you put in it's face. You should have no trouble there. But you're on your own for the other one. Boa constrictors are not my cup of tea.

Boa's arent picky... I can go from frozen to live to smaller or larger without issues.. they are not picky at all.. make them feel safe and then try again

EEK! I hope it goes as easily as you all suggest. I'm hoping I won't have a wasted 20 rats, and 100 fuzzies on my hands. Not that money is the issue here, the issue is the well-being of my snakes, and it absolutely stresses me out when they won't eat. I really hope things go smoothly in their transition and that they'll take up eating when Sig the sand boa is settled in, and maybe a bit more time for Odin the BCI, and when the proper feeders arrive. I've heard from a lot of people that BCI's are practicall garbage disposals and will eat about anything, so I was shocked when he turned his nose a few times to a mouse, and even a chicken broth covered one. Sig may have no problems, I'll have to wait and see after his acclimating period. Keep the great ideas coming!!!

OOPS, I keep accidently refering to Sig as he, or him. When consensus and the previous owners say she is well, a she. haha.

IMO with fostering snakes over 5+ years, I just assume they'll take f/t. most do right away. sometimes you have to be stubborn awhile, but as long as the snake has good body condition, you can wait them out if they don't initially take it.  and Leah makes a good point - wait awhile for them to get good and hungry :P  most of the time once they take it, they'll always take it.

GREAT NEWS! Today Odin the BCI was very active roaming his viv all day, so I thought Hmmmm, maybe this would be a better time to try and feed him instead of while hes buried under his substrate sleeping sluggishly. I thawed out a mouse. Did the twirl, the whirl, the wiggle, and the wriggle with my tongs and the mouse. No such luck. He literally hid from the mouse burying his head under his body, under his substrate, anywhere he could avoid the mouse at any cost. Frustrated I thought "FINE!" But this attempt decided to leave the brained mouse on a flat rock in his enclosure, and leave him alone with it overnight. He ignored it for 20-30 minutes. Then I noticed him gobbling it up! So while he was swallowing the 1st mouse I hurried and thawed out a 2nd one to try to get to him as quickly as possible before he lost feeding interest. Again, he wouldn't take the brained mouse from the tongs, but I only tried for a moment then laid the mouse on the rock and left him alone, and this time I turned the lights out, something that had slipped my mind to do before. I turned on the lights 5-10 minutes later to see if he was even paying attention to it, and the 2nd mouse was gone too!!! I'm ridiculously relieved that he went from live rats to temporarily mice, f/t mice at that. I just had to figure out what his eating style was. Now I hope the transition goes as smoothly and swiftly with Sig the Kenyan Sand Boa, too. I'm also going to get all of my snakes on the same feeding schedule (I think) when the frozen feeder order arrives. Though I'm doubting Lars my male Ghost Corn will be eating anytime soon, because I tried everything you could think of last spring to get him to eat, trying every 2 weeks to no avail and he went 127 days fasting. Wish me luck with Sig!