In one of my presets, I use the Compressor block set to the Compander type into a Volume block on Swell mode. The settings I use in the compander are Ratio: 10, Time: 10ms, Transients: -3, LookAhead: 0. This removes enough of the pick attack and makes the swell behave more like how I want it to.
Unfortunately, you are going to have to learn to "adjust to taste" as your guitar, amp selection, etc will have a huge impact on where you need to set this. "Transients" ARE the attack of the note, if that helps. I would start with the defaults with the Compander (4/10/0) and lower the transients knob until it removes the amount of attack you want. Then, if you need "more" at the level you are at, increase Ratio to make the effect greater.