The light fixtures where the panes of glass come out are the best. Yes, some have metal tabs and require caution but there are many that just slide into virtually indestructible metal grooves.
I then take these pieces of glass out and clean them all at once in the back of the van using Spray Way glass cleaner... scrub with a terry towel, dry with a surgical towel, and detail with a second surgical towel. The ones that can come apart like this end up looking brand new... I attached a picture to show one recently. If they do not come apart, use the same process but just do it with the glass in place. Just be sure the light is secure; keep a hand on it to hold it steady.
I only charge around $6-8 each for these, when you do more than a couple at once they go very quickly.