It is not easy to use standard bent feeler gauges for valve clearance inspection and I would think a 90 degree bend would work better.  Has anyone found 90 degree gauges in the correct size?  I found some sets used for big diesel engines but the smallest is 0.008" and they are needed down to 0.004" (0.1 mm).  There are some straight brass gauges.  Do they bend better than stainless steel?     

You can bend a standard feeler gauge if you warm it up and bend, keep the radius shallow and the blade won't snap. 

I've done this when setting tappets on large diesel truck engines when the tappets are buried.