You can shake off the rust by making sure you warm up before playing, it ALWAYS makes you play better.
Do chromatics in different patterns, like:
| 1 - 2 - 3 - 4
| 1 - 3 - 2 - 4
| 1 - 4 - 3 - 2
| 1 - 4 - 2 - 3
Do it as slow as you need to, and build it up as you go. Don't turn off the metronome.
My best practice when I'm training for muscle (symmetrical shapes without focus on much scales) comes from having a metronome on through a headset and playing in 10 to 20 mins increments.
A practice routine that'll get you back in the zone and even move forward is:
10 mins - Chromatics and warm up
20 mins - Alternate Picking
20 mins - Economy Picking
This will get you well in shape, and you can do those separately through your day when you have the time. Once you're warmed up you remain warmed up until you sleep so you can warm up and then play hours later as long as you haven't slept your muscles are still ready to rowk.
I use this routine and it works magic for my tastes and keeps me tight.
Hope this helps.
Hadi