A Bristish Columbia hunter here so not sure if any of this would apply where you are hunting, but I do most of my elk hunting solo. I'm not in any way an authority on calling or an elk expert but have done ok.
Be flexible. If it isn't working for you, try something else.
I do bugle but sparringly as I hunt higher pressure area and typically reserve my bugles for pre dawn location or last hour of daylight, or on the odd occassion late at night if I haven't found them yet (I've found they can be quite chatty between 10pm and midnight in my area when they are very quiet during the day, like they know the daytime bugleing is BS ). If I were in a less pressured area, I'd probably bugle more then I do.
I do well with cow talk and hot cow call. I can whip out a pretty loud cow call and get bugles in response but do also call in allot of silent elk. When I get a bull talking, unless I know the bull is within a couple hundred yards, I move very fast to close the distance (and I'm not quiet about it).
I ALWAYS avoid setting up in any area that an elk can survey from a distance. I want to make him come looking for the source of the sound. You can also use terrain features to your advantage to accomplish this.
Stalking in on elk is also easier solo. If you find good sign in dark timber, this is a real good technique. As is sitting on wallows if you find a hot one.
In the area I hunt, I do my best to get into spots others don't and do whatever I can not to sound like the other hunters cruising the area. . Like I said, I hunt a high pressure area and when everyone is screaming away on bugle tubes, I often put mine away and put distance in between myself and them.
I still have my old Renzo's cow elk decoy that is with me whenever I'm bowhunting. Have used it successfully on several elk and had them come in, lock onto the decoy and give me a great shot. A great tool for a solo hunter, (but can be a pain to yard around at times).
Have had good luck late in the evening. Shot 3 within the last 10 minutes of legal light. In my experience, they just seem very willing to come right in at this time of day. But word of caution here. If you are not prepared/willing to work solo in the dark buthering and packing, don't pull the trigger or loose the arrow. It's not exactly enjoyable solo task when you are elbows deep late at night in griz country.