https://www.viabtc.com/tools/txaccelerator
The downside of using this is that it gets easily full after a few minutes kasi 100 lang yung ina-accept ng pool every hour (e.g., 12:00-12:03) to be precise. This services only offers to accelerate your tx to be included in the next block they are currently mining, so swertehan din talaga.
As per the RBF or Replace-by-fee, only a handful of bitcoin client I think supports this feature and it is Electrum to be specific. I tried it personally though using testnet, the RBF function really works if your transaction is stucked in the bitcoin network due to low tx fee. As per my experience, RBF can only be used if the transaction is still unconfirmed, meaning it is still not added into the next block, only by then RBF can re-broadcast the tx with a higher tx fee (sat/byte) para maisama na siya sa next block.
CFFP, medyo wala pang idea. And I think this is similar to RBF eh.
Merong ginawang guide si Zepher on accelerating your transaction for free, most of the sites na binigay nya ay gumagana pa din pero recently nung gagawin ko sana ay hindi na gumagana yung paraan niya para makuha yung hex format ng isang transaction, ito kasi yung kailangan mo para ma broadcast ulit yung transaction dahil lahat ng Bitcoin accelerators ay kailangan yung hex format ng transaction.
Dati ito kailangan itype mo sa dulo ng url ng tx-id mo para ma re-direct ka sa hex format nga tx id mo
Pero since nag-bago na yung Blockchain.info at naging Blockchain.com parang nag-bago din yung format nila para makuha yung hex format ng isang tx id. Now if ilagay mo yung "?format=hex" sa dulo ng URL ng tx id mo ay either ma reredirect ka sa same page ulit or bibigay ka ng "Oops! We can't seem to find the page you're looking for". I'll keep you updated kung makakita ako ng ibang paraan para makuha yung hex format since ito lang naman kailangan mo para mag-accelerate ng mga transactions ng hindi nag-babayad.