Still the remaining question. There are tools/plugins to re-balance the channels. But how you do the inital fund of the "other side of the cannel" (incoming?).
You can gain incoming liquidity in a couple of different ways:
- pay for some service/goods,
- use a third-party service to exchange your off-chan coins for on-chain ones (ex.
Boltz,
ZigZag),
- contact your channel partner and do the same as above (it will be much cheaper, but there's more trust involved),
- circular rebalance (only possible if you have at least two channels; one with lots of inbound liquidity and the other one with outbound capacity).
Also, c-lightning is currently the only implementation which supports dual-funded channels. Such channels might be balanced as soon as they are opened as both parties contribute funds. Note that this is still an experimental feature and very few nodes support it. I opened about 3 dual-funded channels with other bitcointalk members.