Beyond memorisation and time, how can you master Grammatical Gender in Spanish?

Question

1. How can adult L2 learners learn, master, and remember Grammatical Gender more efficiently? Memorisation and time do not improve advanced L2 learners.
2. Are there shortcuts or patterns or rules for gender assignment, which L2 learners can try to comprehend, or at least memorise more efficiently than memorising the gender of each noun?
3. Are there any books or resources or studies that have discovered or exposed shortcuts or aids (as queried in 2 above)?

_{Unfortunately, this problem also afflicts this learner.}

Answer 1

I may have answered my own question. The short answer is: Appeal to and research Linguistics!

For example, I Googled "spanish nouns gender assignment" which revealed many Linguistics articles, such as:

Spanish Gender Assignment in an Analogical Framework by David Eddington,
pp 49-75, Journal of Quantitative Linguistics Volume 9, Issue 1, 2002 (PDF here) (Draft here)

Then consult Citations of this article and this article's References (at the end) to find even more Linguistics research, the latter of which is first referenced in the Introduction:

Previous studies of Spanish gender fall into one of three major categories: 1) In the pedagogical approach (e.g. Bergen, 1978; Bull 1965; Teschner & Russell, 1984), the emphasis is placed on dividing Spanish nouns into masculine and feminine groups based mainly on their final phonemes, and listing the most common exceptions to those groups. This categorization is made to facilitate the acquisition of Spanish as a second language. 2) In the descriptive approach (Teschner, 1983; Rosenblat, 1952), on the other hand, the interest is in finding systematic correspondences between nominal gender and phonological patterns in Spanish words. 3) Generative analyses (e.g. Harris, 1985, 1991; Klein, 1983, 1989) strive to describe gender in terms of a rule system that derives a word's final phoneme(s) given the word's inherent gender and a set of abstract assumptions about the word's underlying structure.

Although each of these analyses may be valid in its own realm of inquiry, none of them have as a goal to determine how native speakers may go about assigning gender when syntactic clues such as gender-marked determiners and adjectives are absent. Given the mentalistic vocabulary often employed in the generative literature (i.e. processes, derive, language acquisition, production, etc.), one could gain the impression that such analyses do explain how native speakers assign gender. (This contrasts with the clearly descriptive goals of the pedagogical and descriptive approaches.) Generative accounts may be elegant representations of linguistic structure, however, their relationship to the psychological mechanisms that play a role in actual language usage is dubious (Chandler, 1993; Derwing, 1973; Eddington, 1996; Lamb, 2000; Skousen, 1975). In addition, some researchers have clearly stated that generative accounts are simply not intended to be taken as models of linguistic performance (c.f. Kiparsky, 1975, p. 198; Chomsky & Halle 1968, p.117; Bradley. 1980, p. 38)

Answer 2

I'll try to give you an answer to clarify your doubts:

1 and 2- Usually (that is to say 95% of the cases) female gender ends with an -a in a singular and with -as with plural forms.

Example:
La mesa tiene 4 patas. 
Las mesas tienen 4 patas.

In male gender, words usually ends with all other vocal and also adding an -s with plural.

Example:
El palo de golf es de hierro
Los palos de golf son de hierro.

Of course there is a lot of exceptions but usually with that form you will be able to recognize the gender easily. The other way, as you can imagine, is to practise and try to remember the words.

3- Of course there is a lot of information and resources. Unfortunetely I'm not capable to recommend you any of them, I'm a native spanish in Catalonia and I'm not sure which books are better for a student of L2 or others.

Hope it helps a bit.