If you’re technical, you can do it yourself. If not, others like nostr:npub1rxysxnjkhrmqd3ey73dp9n5y5yvyzcs64acc9g0k2epcpwwyya4spvhnp8 are setting up white glove services to help linked below. And yes - members of mint a can transact with mint b - (transacts through lightning) and seamless for users.