In part the problem may be about think that learning to read bass clef means memorizing the letters for the lines and spaces.
That may seem the obvious way that a clef is read, but another way to read is by the relative movements. Consider a melody starting on
F3 - the
F on which the bass clef is centered. Instead of reading something like
F C E G, read like
start on F, P4 down M3 up m3 up....
Combine that with reciting the letters ascending and descending in thirds (
B D F... and
B G E...) and in fifths (
B F C... and
B E A...). Reciting letters through triad inversion (
A C E, C E A, E A C...) is a good method too. This is the thing to memorize as fixed and concrete. This should be internalized.
Putting both together, if a clef tells you the middle line is
C and the next note ascends a fourth the next note is
F. Knowing the specific letter comes from the internalize knowledge of the letter sequence of descending fifths.
In a way, you don't need to know the letters of the notes provided your move the correct interval distances. Again that may sound odd, but if your music reading starts to involve lots of different clefs or transposing on the fly, you start to develop a much more fluid sense of what the letters of the staff are.
After gaining experience reading bass clef you will end up memorizing lines and spaces. Like the bottom space is
A, the middle line is
D, etc. But it's probably better to let that come naturally instead of through rote memorization or mnemonics.
I don't use bass clef that often... Are there any specific exercises...
One way to look for material is get vocal or contrapuntal music where the bass part will have greater melodic quality that homophonic bass. Cut to the chase and get Bach's 371 Harmonized Chorales and just play the bass parts.