I've tried numerous free transaction accelerators in the past because of desperately needing to confirm certain transactions. The one single accelerator that actually helped is only ViaBTC's accelerator[1]. Pretty hard to get in to it though as a lot of people are using it, effectively flooding their website; sometimes even crashing it.
[1]
https://pool.viabtc.com/tools/txaccelerator/Viabtc works for the people who tried to accelerate every first 100 members using the accelerate tool. Other than this you will find the antpool accelerator which is used for the same use and many of the users reported this also works better like viabtc.
You cannot able to use the acceleration tool use successfully means send that to people who is dedicatedly working for it services section.