I don't think the OP needs to use any transaction accelerator, the last time I checked this accelerator service shouldn't be trusted and it better to bump the tx Fee.
ViaBtc works, it has worked for hundreds of members and I've used it just two days ago and managed to get one tx confirmed in a block mined by them.
So, what happened when you used it that made you think you should not trust it?
When I said not to trust them, I mean I don't believe it their service really work.
What happen is that I have to wait for some hours before my transaction was accepted by them due to their hourly limit, in the end, the transaction was not mine by them and it hurt cause I have spent some hours before locking in the tx though it happen long ago but will try out whenever I have stuck tx cause people are making a positive comment about there services this day