Interlinear text with partial translation

Question

I've got my file set up to create an interlinear two-language text (for this example using Russian). I created it using various code-snippets from this very same site.

The problem is that the interlinear texts already discussed here all deal with situations where entire sentences or paragraphs are interlinear, like my current code.

But what I want to do is have the primary language and then simply designate a word/s for interlinear glossing (i.e a gloss for a single word in a sentence rather than the whole sentence itself).

In this image I gloss every word except one.

\newenvironment{interlinear}%
{\begin{russian} \begingl}%
{\endgl \end{russian}}%

\begin{document}
\begin{interlinear}

\gla Now {\hspace{0em}} {the possibility} {to print} simple documents 
with English and Russian. //
\glb Теперь есть возможность печатать простые документы с английскими и 
русскими.//

\end{interlinear}
\end{document}

As you can see I can use h-space to leave a word blank. But I want to leave most blank, like this:

\gla {\hspace{0em}} {\hspace{0em}} {\hspace{0em}} {to print} 
{\hspace{0em}} {\hspace{0em}} with {\hspace{0em}} {\hspace{0em}} 
{\hspace{0em}}. //
\glb Теперь есть возможность печатать простые документы с английскими и русскими.//

The thing is that even if I'm not using h-space effectively, obviously this doesn't seem to be an efficient or appropriate method.

So is there a way to do something like "Это простой{^simple} Русский язык" and then get the English gloss for that single word?

Edit: the packages I'm using:

\documentclass[draft, a4paper]{article}
\usepackage{polyglossia}
\setdefaultlanguage{russian}
\setotherlanguage{english}
\newfontfamily\russianfont[Script=Cyrillic]{Lava Pro Reg}
\newfontfamily\englishfont{Equity Text B}
\usepackage{expex}

Answer 1

The command

\translate{lower word}{upper word}

will insert lower word at the current position, with the upper word in small print above it. The command is defined as

\newcommand\translate[2]%
  {\begin{tabular}[b]{@{}c@{}}
   \footnotesize #2\\
   #1
   \end{tabular}%
  }

Modify as needed; you maybe want to abbreviate the macro name if you need it frequently.

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T2A]{fontenc}
\newcommand\translate[2]%
  {\begin{tabular}[b]{@{}c@{}}
   \footnotesize #2\\
   #1
   \end{tabular}%
  }

\begin{document}

\noindent
\translate{Теперь}{Now}
есть
\translate{возможность}{possibility}
печатать
простые
\translate{документы}{documents}
с
английскими
и 
\translate{русскими}{Russian}%
.
\end{document}

If you have lines without any translations and want to have the lines uniformly spaced, increase \baselineskip.

...
\baselineskip26pt
\begin{document}
...

Answer 2

Perhaps I misunderstand your problem, but selective glossing is simple to do with the existing glossing packages. Here's an example using ExPex, which I think is most suited for your purposes. I've used the centred glossing settings from How to do centered interlinear text in LaTeX. To selectively gloss words you just need to use {...} around the groups that are grouped together, and make sure that the number of groups in the source line matches the number of groups in the gloss line.

\documentclass{article}
\usepackage{expex}
% Settings from https://tex.stackexchange.com/a/224154/
\lingset{everygla=\footnotesize\sffamily, % formatting the numbers in the gla line
    glwordalign=center, % center alignment within glwords
    aboveglbskip=-0.4ex, % narrows the vertical gap between the gla and glb lines
    glhangstyle=none, % no hanging indent
    glspace=!0pt plus .2em, % widens the allowable space between glwords to avoid overfull lines
    glrightskip=0pt plus .5\hsize, % widens the allowable space between the right margin and the end of the last glword on a line to avoid overfull lines
    everyglb=\textrussian}

\usepackage{polyglossia}
\setmainfont{Linux Libertine O}
\setmainlanguage{english}
\setotherlanguage{russian}
\begin{document}
\exdisplay
\begingl
\gla Now {} {the possibility} {to print} simple documents with English and Russian.//
\glb Теперь есть возможность печатать простые документы с английскими и 
русскими//
\endgl
\xe
\exdisplay
\begingl
\gla {}  {to print} {} with {}//
\glb {Теперь есть возможность} печатать {простые документы} с {английскими и 
русскими}//
\endgl  
\xe
\end{document}