[Quinlan]

Instead of trying to get the .04 feeler gauge in right away, try backing the adjusting screw out a couple of turns. That will provide lots of clearance, especially if you reach in and pull back the part of the lifter with the screw in it. That will allow for plenty of room to let the regular .04 feeler gauge slide in easily. Then tighten the screw back down until you get the elusive "slight drag". You can double check it with the go/no go method.
Double checking takes a little longer, but I like the peace of mind it provides.