Replenish the ink of a fountain pen by dipping
If the fountain pen has any kind of (suction) pump, then you will need to use the said pump.

The capillary effects alone will not have the power to fight the weight of the ink itself.



My personal hack

I have a fountain pen with one-time-use cartridges. It came originally with a very long one (compared with what is usual in shops). Because I did not want to purchase so much plastic (the small one time use cartridges), I decided to use the original one. To refill it I use a syringe (dedicated specifically to this purpose) to transfer ink from the ink bottle to the cartridge. I use it in this way for more than 20 years without any issue. The original cartridge, even though it was designed to be one-time-use, still fits properly, without leakage, to the pen.