most of the type-design world is moving towards a ufo-centric workflow. ufos are basically simple to grok xml files defining bezier curves. Adobe's AFDKO (Adobe Font Development Kit for Opentype) supports ufo and generates from them full-fledged otfs. Another great resource is the more recent fonttools fork on github at https://github.com/behdad/fonttools .

I used to like fontforge, it's a fine application, but the move to ufo has made it easier to apply older svg-based tools to editing splines and saving out as ufos. here's a free application, it looks promising! https://github.com/trufont/trufont .

finally it's worth looking at https://github.com/LettError/MutatorMath which has lots of the tools for interpolating masters. There are actually loads more resources and, if you are short on time or attention, my guess is that the tightest workflow will be coming to Robofont (which hovered around 500 euro for a while).

Still, it's all very accessible to you even outside of fontforge and all the libraries for modifying ufo-style paths are freely available. take a look, it seems very fractured, but i think it's a nice distributed workflow all things considered given the final output.