I have used:
Disposable foamy plugs - which made it quieter, duller and less comfortable. They needed re-seating in my left ear every hour or so.
Docs ProPlugs - which were great for drums, but not so good for sound, as they had a far from flat frequency response. I liked the several sizes approach.
ER20s - which were better for sound work, but I found that the plug in my left ear consistently worked itself loose during drumming, requiring refitting every few songs. Also I found the fit less comfortable than the ProPlugs.
And then at LIMS, I splashed out and had some ER15s made. These moulded plugs are so comfortable I don't notice them, and they stay put for longer than any others I've tried. The sound is very clear and transparent, though the effect of hearing one's own bloodstream through the head seems greater. I also feel that they make things sound a little compressed somehow, making a mix a bit lifeless.
I could happily mix with my ER15s in, though I would feel the need to remove them occasionally to check for harshness as they seem to smooth the highmids a little and for volume.
[edit]
I should have mentioned that (as with all plugs) the ER15s make the mix seem sub heavy, as they cannot attenuate what you 'hear' through bone conduction and sternum thumping.
Perhaps wrap some large cell foam around your chest?