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If you can afford it, Fluke is probably the best brand. I use a "Brymen 202", which seems to perform quite well.
A capacitance symbol on a multimeter may either look the same as a capacitance symbol on a schematic (one straight line and one curved line), or it might have the letters nF or uF.
My Brymen meter costs about AUD$130. A "cheap" Fluke meter is around AUD$250.
Be aware, though, that for measuring very small capacitances, like those in trimmer caps, a multimeter may not provide great accuracy. You may also need to "zero" the meter, due to internal capacitances (on mine I do, on Flukes there is no need).
You can also use an 'LCR' meter, which measures inductance, capacitance and resistance.
Also don't forget, that to measure the capacitance of your trimmer, you need to isolate at least one leg from the rest of the circuit (ie, desolder it from the board).